I have only a limited experience so far but had a range of sails, all used on the same boards. I had a tushingham x15 that really suited one board but no the other. My front foot kept coming out of the strap on the bigger board yet it didnt when using my simmer scr. On the smaller board it was great (mistral sl95rd) and I always felt comfy, yet the simmer scr's didnt feel very comfy. The difference in boards - one was long and thin the other short and fat, the mistral had a more pronounced rocker, sharpness of rails etc seemed similar. The mistral was more pic tail as opposed to wide back end.

I think without a doubt certain boards and sails are well suited, and others would need a fair bit of tweaking to get the best out of them. I have now gone onto Hot Sails Maui GPS race sails and Exocet RS slalom boards, they feel like they were made for each other but have only had a few sessions so difficult to comment why yet.....there is no wind here in western europe, its crap at teh moment, divorce papers will be on their way soon ;-)

Eric loots made some comments recently about footstrap placement and he did comment about the suitability of certain sails with boards.
www.speedsurfingblog.com/2012/01/close-footstrap-position-best-read-this.html he also has a lot of other articles that touch on this subject