I use marine velcro to move my compass from one boat to another. I confess I
don't usually have one mounted at all.

I also "dummy cord" the compass to the boat as I have knocked it off a couple
times (surf and paddle strike).

A friend mounted a quality compass on a wood block. The underside is sculped
to match his deck ridge. He then uses bungies with clips to hold it in place.

Brian Blankinship