Yes, hulls matter when getting up, but again those shapes have already mostly been optimized with the fat sterns and modern rocker profiles.

The flying phantom has 10' carbon beams, >32' carbon rig and full carbon hulls, built by the #1 F18 builder for quality in the world. It is equally as powerful as the F20C and the build quality is likely better (read: stiffer=faster on foils). Again, I'd take the flying phantom over a full-foiling F20C in anything above about 8 kts of breeze.

Yes, the F20C is a good retrofitting platform, but again a lot of work and $10K to add foils to a boat that is just as expensive as the flying phantom to begin with. It doesn't make economic sense unless you find a F20C for less than $20K.