Twin Rudder lead and sizing?

Dear All,

I am currently facing the task of sizing a twin rudder system for a sailing yacht.
My current method has been to heel the boat at an expected heel angle (IE 20°) and establish an ideal value for lead, then size rudder area (projected on the heeled plane) based on said lead.

I am using the Nomoto method: (Extend the keel to the DWL to account for hull contribution, use a rudder reduction factor of 0.4 and take the individual CLRs about the foil's quarter chord line). This is mentioned both in Principles of Yacht Design and Fabio Fossati's Aero-Hydrodynamics book.

I am not entirely sure on this method since in these books it only mentions single rudder systems, I also immagine that a rudder which is offset to leward will produce a "bear-away" moment, thanks to its own drag and I am not sure how much it contributes to lead calculation (probably very little).

I have searched a bit on the past few days but I could not find much on papers nor on this forum.
wanted to hear your thoughts.

Hopefully I am just overthinking over a simple issue.

Cheers,

Claudio