: The only question is whether or not the plywood can take all that compound
: bending, the akas will be curved as well as tapered

there is no compound bending in this situation. in its simplest case with a constant angled ama cross section (size can change up and down and/or taper if you wish)you are only contrained by the ability of the ply to take the bends. so test first then choose multiple plies or glass layers of what works. at it's most complex, you'll be introducing some minor twist here.

the gullwing curvature and member size and taper variation will be determined by the back vertical web, so easy to build that first, then brace to keep shape and either add a temp curving central spine or multiple triangular shape forms and make 2 temporary cardboard or doorskin templates - one for the upper and one for the lower surface as a cutting guide.

seal and glass the inner surfaces of each and stitch together, drainage in low pts. outside seam and glass to yr hearts content.

prob best to inside seam the lower panel in place, then stitch/glue/seam the top as you willget a more durable and moisture resistant inside seam corner.

also drain and vent.

i'm sure you have, but looking at gudgeon book or some multihull sites might give better guidance.