well i ride my 9 from about 16/17 (but at that im struggling) to anything around 24 before unhooking becomes hard and i can hold it hooked in up to about 28 30 before having to play with depower.

the 11 wouldn't pull you up at 80k in 14 knots, it would be able to get you up and riding etc but depending on what kind of riding you want to do you may want to consider a 13 or perhaps a envy 12. if you going to ride a surfboard and crusie around slayin waves or chop what ever then the 11 would work, if you want to just cruise around do lil boosts then the 11 will work, but if you want to unhook and progress, or get bigger floatier jumps etc then the 13 would be a good choice, the large sizes are very fast anyway so you won't dislike the 13.

yes, y have a doubt because i have a north vegas 12 (windrange 13-25, north web), but i start kiteboarding in 10 knots, in a 132 x 41 kiteboard, have more power
the vegas compared to hifi in the same size ??

i found the hifi has a bit more static grunt as such, but it can still be worked to gain speed.

you will probably gain like a knot from the hifi's bottom end but in the end that will come down to which kite you like the feel of more IMO