I agree that they should be allowed, even if they are more difficult to extract performance from (aka, rewards those that spend the most time on the water). The cost of retrofitting them to existing boats is an issue but best I can tell curved foils only cost slightly more than the newest high aspect ratio boards in the F18 class. This makes sense since the proper tooling costs are very similar and the only change is in the amount of material needed in the curved foil (more) so the price reflects the material difference and possibly the slight increase in labor needed. I don't see why this would be any different in the F16 class. If there are concerns over performance, stick with trunks like those used on the Bimare V1R that can accept curved and straight boards.