RE: Serenity Q
I was using a 7.4 sail (which I've used for nearly all my Serenity sailing), and probably a little less wind. I'm wondering if by using a larger sail you are already getting lots of forward drive to push the nose down, so when you move to the front as I did, their is too much force forward. I plan to try my 9.5 one of these days.
BTW - 10.6 in 12 knots seems like a lot of sail for Serenity! I usually switch to my early planing board before that.