I have a 43DS and thought (briefly) about a staysail. After looking at the deck structure forward where it could be mounted I realized that quite a lot of additional reinforcing would be needed to support the loads this sail would take (my intent was to use it as a storm trysail). The cabin deck has enough openings in the leads on my boat to take an additional
furling line and could support 2 more sheets, but the angles would be wrong so these would also have to be led parallel to the Genoa
lines and the added hardware would make walking forward tougher.
It would be great if your engineer could find a viable solution, but I'm not too sanguine about it.