[Solo]

I'm windsurfing ok with Formula board, and doing good with a Carve 111,
but sometimes, with the Carve, i'm going through chops and the fin looses the grip and i end sliding sideways.
What's the solution to that problem? I'm trying to put the hips as forward as i can, and to have my weight in the forward foot, but even then, as i get confortable, i go thorough a chop (don't even realize the fin got out of the water, but it happens again!!
What should i do?
Solo