[tevake]

Its a good idea to tape the fin right at the point where it sticks out of the box so the sanding is just in the area meant to be inside the box. Sand just till it will go in with some effort. Don't want it to be loose in the box. If there is split pin in the fin you may be able to tap it to one side so you can sand easily. Then recenter the pin..

The older fin type of fins could be slid fore and aft for tuning. This often needs the fin to be rotated out of the box except for the corner with the pin to be able to move it. Then when rotated back into the box it becomes very tight. Hope this helps rether than confuses the issue.

Cheers Richard