Yeah, iSonic 131 seems to be super wide for it's volume. Even the 121 looks massive in photos. What about formula experience? I'm guessing it doesn't plane as easily as the normal formula due to construction in Tufskin...
Apparently it's cheaper though... I can't find a price online for it.
I will try to test out some equipment, right now the wind is perfect at my spot for formula, too light though for my 106l.
JP Super-X 106l, North F8 Ram: 5.8m,