Same weight as you and I use iSonic 117 Wide with 7.7/8.6/11.0 m2 sails. Planning at full speed in winds from 7 up to 18 knots.
Tried iSonic 127 and it's clearly 1 size larger than iSonic 117 wide. However, I did not experienced any gain in lower planning threshold with lighter winds IMHO.
With 9.2 m2 sail as largest and for your light weight, no need to go to iSonic 127, the 117 should be plenty enough. What is your other high-wind slalom board(s) ?
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