How to avoid "spin outs"?

[TomG]

I still experience too often "spin-outs" (the fin doesn't "work" anymore and the board moves sideways). I believe that I put too much pressure via the rear foot and strap onto the boards. I have tried to straighten my front leg a bit more and almost pull the back foot towards me, which has given some improvement. However, I find it difficult and feel not all the time that my body has good poition / "posture".

Are there any tips that you could give to prevent this phenomena?

Thomas