Trillium Trading Takes 5.4% Stake in Rubico (RUBI)

Rhea-AI Filing Summary

Rubico Inc. Schedule 13G filed by Trillium Trading, LLC reports beneficial ownership of 175,000 Class A Ordinary Shares, equal to 5.4% of the class as of 06/10/2026. The filer states sole voting power and sole dispositive power over the reported shares. The filing is signed by a compliance officer on 06/11/2026.

Insights

Corporate Governance Analyst

Reporting entity holds a passive but notable 5.4% stake.

The Schedule 13G shows Trillium Trading, LLC beneficially owns 175,000 Class A Ordinary Shares with sole voting and dispositive power as of 06/10/2026. Under proxy rules, a >5% passive holding requires disclosure but does not itself signal control.

Watch subsequent filings for any change to Form 13D status or amendments that would indicate active intentions; timing for such disclosures is set by the securities rules and would appear in future filings.

Market Structure Specialist

A single 5.4% holder can create visible ownership concentration without immediate action.

A 5.4% position can affect perceived shareholder base and potential block trade interest; the filing lists sole voting and dispositive power, which matters for proxy aggregation and outreach.

Subsequent trading or additional disclosures by the holder would change market overhang; current filing simply documents ownership and authority as of the stated date.

Key Figures

Filing date: 06/10/2026 Beneficial ownership: 175,000 shares Percent of class: 5.4% +2 more

5 metrics

Filing date 06/10/2026 Schedule 13G date line

Beneficial ownership 175,000 shares Class A Ordinary Shares

Percent of class 5.4% Percent of Class A Ordinary Shares

CUSIP Y1250N123 Class A Ordinary Shares CUSIP

Signature date 06/11/2026 Signed by Compliance Officer Louis Capone

Key Terms

Schedule 13G, Beneficial ownership, Sole dispositive power, Sole voting power

4 terms

Schedule 13G regulatory

"Schedule 13G filed by Trillium Trading, LLC reports beneficial ownership"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

Beneficial ownership regulatory

"Amount beneficially owned: 175000 (b) Percent of class: 5.4 %"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

Sole dispositive power regulatory

"Sole power to dispose or to direct the disposition of: 175000"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Sole voting power regulatory

"Sole power to vote or to direct the vote: 175000"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

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Available on EDGAR 06/11/2026 - 10:59 AM Accepted by SEC EDGAR 06/11/2026 - 10:58 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Rubico Inc.

(Name of Issuer)

Class A Ordinary Shares

(Title of Class of Securities)

Y1250N123

(CUSIP Number)

06/10/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): Y1250N123

1

Names of Reporting Persons

Trillium Trading, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 175,000.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 175,000.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

175,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.4 %

12

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Rubico Inc.
(b)	Address of issuer's principal executive offices: VAS SOFIAS 1 & MEG. ALEXANDROU, ATHENS, GREECE, 19002
Item 2.
(a)	Name of person filing: Trillium Trading, LLC
(b)	Address or principal business office or, if none, residence: 417 Fifth Avenue, New York, New York 10016
(c)	Citizenship: Limited liability company organized under the laws of the State of Delaware, United States of America
(d)	Title of class of securities: Class A Ordinary Shares
(e)	CUSIP Number(s): Y1250N123
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 175000
(b)	Percent of class: 5.4 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 175000
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 175000
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Trillium Trading, LLC

Signature:	Louis Capone
Name/Title:	Compliance Officer
Date:	06/11/2026

FAQ

What stake did Trillium Trading report in Rubico (RUBI)?

Trillium Trading reported beneficial ownership of 175,000 Class A Ordinary Shares, representing 5.4% of the class as of 06/10/2026. The filing shows sole voting and dispositive power over those shares.

Does the Schedule 13G filing indicate control of Rubico (RUBI)?

The filing documents beneficial ownership and sole voting power for the reported shares but does not state an intent to control. Schedule 13G filings typically indicate passive investment unless later amended to a Schedule 13D.

When was the Rubico 13G signed and filed?

The excerpt shows the filing date line 06/10/2026 and a signature by the compliance officer dated 06/11/2026. Those dates anchor the reported ownership level.

What voting or dispositive powers did Trillium disclose for RUBI shares?

Trillium disclosed sole voting power of 175,000 shares and sole dispositive power of 175,000 shares, with no shared voting or dispositive powers reported in the filing.

Will this Schedule 13G trigger further disclosure from Rubico (RUBI)?

The Schedule 13G itself is a disclosure of ownership. Further filings would occur only if the holder's status or intentions change (for example, converting to a Schedule 13D) or ownership crosses regulatory thresholds requiring additional filings.