Have to agree with Dan Ward, too many formula classes just divides us up into tiny sub-classes, might as well stay open class, HOWEVER :
If all Formula classes can strive to be equal or very close in performance, this could create ONE Formula class in the future. It`s optimistic, but possible. Only way to acchieve this is to exclude the manufacturers from decision-making positions in the classes, and ask the SAILORS what they want, create the Formula & then tell the manufacturers what sailors want. Will never happen because the manufacturers need to control the market in order to survive, EXAMPLE :
Hobie would not build a F16 boat that is equal in performance to F18, as it would erode the support base for their F18 product, unless there is sufficient market share for both. If Nacra made their F17 equal in performance to F18, same problem, so they will have to differentiate the two, probably by making F17 a single-handed only boat.
So where to now ? create Formula classes that each have appeal to their own target market, but make them equal or very close in performance to eachother, ie F16 ISAF rating = F18 ISAF rating, a good place to start. If F17 does the same, we have 3 formula classes that could compete on equal terms. This would unite sailors who choose different platforms for whatever reason. The one problem with this is that I can`t see F18 sailors welcoming the thought of being beaten by 16ft or 17ft boats, so they will want to stay separate. I can`t see F14 competing on equal rating to F16/17/18, or F20 either, so F14 & F20 will have to play on their own. But F14 could declare H16 non-spin & P16 non-spin as their "target class rating", so should strive for ISAF rating of 1.16, which I think is realistic, this would allow them to include H16 & P16 sailors in their foundation boats. This would create larger fleets racing on elapsed time, main objective of Formula Classes. One of the objectives of Formula classes should be to INCLUDE as many existing cat classes as possible, even if the classes are different lengths, as far as I know I-17 & FX-One are INCLUDED in F16 class as their performance should be very similar.
I would propose 3 formula classes, all as inclusive as possible :
-F14 : including older generation non-spin 16ft boats, ISAF rating 1.15-1.17
-F16/17/18 : Allow P18, TheMightyHobie18 (& Dart18?) with spi, must rate equal to F18 or less.
-F20 : More of an open class, allowing Tornado, SC20, N6.0 etc.

Question : Would F18 sailors in general welcome inclusion of F16 &17 boats at their events racing on equal terms ? Or would F16 & F18 only compete on equal terms at Open events ?
I reckon that`s like asking if Tornado sailors would welcome I-20`s at the Olympics .

Cheers
Steve