Fin or mast track position

[Guest]

Hi
I have a Isonic 125 and a JP 136.

I thought that under hot conditions (+23 knots) the technical side of the Isonic was getting the better of me, as the back side would lose grip and slide sideways. (Nose points into the wind) Now I am doing it with both boards.

I changed the fin down a couple of sizes, but with both boards have the same problem.

Is this a mast track setting, or am I getting too old.

Please help.

Cheers