This might be a recurrent question, which size Sonic-FR do you suggest for a rider on a 140 TT 75kgs ? 15 or 18m ?
The flysurfer reseller told me it was useless to go on 18m with a board below 160cm because on his words: "you cannot transfer the power of the kite to the board".
My current biggest kite is a Vegas 12m (limited low end), usually i don't kite with that kite below 15 knot.
We often have 8-13 knot wind.
I might want to use it on snow as well but that's not a priority.
Also how about the Chrono V2?
I weigh the same as you. I frequently fly the 18 in the winds you describe. I use as small a board as possible, frequently a 130 or 132. A smaller board is just much more fun to ride. I rarely ride my 138cm board with the 18 Sonic, only if the wind is under 10 knots.
As far as using a small board with a big kite, why do you think Toby is using a 129cm board with an 18m Dyno in 20 knots for Airstyle? The smaller board will give you more grip, plus the Sonic has plenty of depower, so you are not going to get ripped downwind unless the wind is gusting well over 20 knots.
Haven't tried the Chrono 2 yet.
My Sonic arrived just after the end of the snow season, so I haven't tried it on the snow yet, but I can tell it will be excellent as I prefer it to the 18 Chrono and 21m & 15m FS Speed 4 Lotus on the water. If anyone wants a 21 or 15 Speed 4, I have them up for sale.