I'm figuring that the difference between full foiling a 30 + 70 kg moth and a partially lifted 107+ 140 kg F16 (for only < 30%) may be an important difference. The F16 will still be carried by the leeward hull for 70% and thus be stabilized. This is basically what the nacra20c and A-cats are doing as well.

Additionally what is the difference between the righting moment of a viper with both L- foils in the water and a single foil in the middle of the viper ? When it comes to righting moment both setups will result in the same overall moment.

Personally, I don't believe that foils are much of a performance gain in most conditions. Hwever the reason I'm interested in them is improved stability of my taipan under spi in big waves especially during long distance racing. For me it is either T-foil rudders or this. This is easier for me to make and try.

Apart from that I'm looking at th following calcs

170 kg crew on my 120 kg Taipan F16
45 kg lift of centrally placed foil
Combined weight carried by bouyancy will then be 245 kg or 110 kg + 135 kg crew.
New rightingmoment will be transformed from 170*3.5+120*2.5*0.5 = 745 kgm
Into 745-45 = 700 kgm = 157*3.5 + 120*2.5*0.5

basically by adding the central foil I expect to get a boat that will partially lift its bows at speed then without thus reduce the dependence of bouyancy to carry to sail loads and wave action.

Secondly I expect to get a boat that thinks that it sailed by a 45 kg lighter crew with the righting moment of a crew that is only 13 kg lighter. The reduction in overall weight ( by 15%) is more then the reduction in righting moment by ( by 6 %).

However, I still don't expect much if any perormance gain except for what is th result if increases stability under spi in waves/ chop