That's right, conditions are often light, gusty (but it's a large lake so it's more consistent than on a small pond) and choppy and I'm looking for a board and sail combination that gets me going early. But I'm not looking for easy freeride cruising but for performance even in light conditions. Not strictly racing but rather flatwater blasting with friends. Formula is too extreme and limited so I'm looking at a large slalom board to complete my current range (59 and 69 wide) that can carry a big freerace sail (8.4 to 9.5, maybe 10 m2). My worry is that the "big" boards such as your 127/131 85cm wide boards may be too powerful for my weight/size and that I may never get the max performance out of them because I can't get enough weight on the fin to make it work properly. Hence my question whether for the above mentioned conditions and sail range I'd better look for an intermediate size such as your 117 Wide (80cm) board or if you think that I could handle the larger ones in the ideal wind range. As stated I sail slalom boards with freerace sails already and like their athletic sailing mode.
Hope this clarifies.
Thanks for your advice !