Rain water coming in through the inside of the mast?
Further to converting from Keel to Deck Stepped Mast:
I''n not a Structural Eng (nor Architect); but I know enough to get myself into real trouble!
1. I don''t understand your reference to "another Panel". What is a "panel" in this context?
2. The "Moment Connections" between mast & king post will have to be at least equal to the Mast Base Moment Capacity (from section modulus).
If the gusseted plates are separated by the deck (newly sealed mast aperture), then deck compression becomes an added factor in the calculation.
Perhaps it might be better to carry the king post thru'' the opening, sealing around it (spec''d to accept horizontal loading), and make the moment connection immediately above the house deck.
If you''re not tired of the subject, your further thoughts will be appreciated.
Regards, and thanx for the GREAT input,,