Stock board is very slick and very bendy - thinking of either a leather top that the Zipfit can bite into or a marine nonskid tape (acrylic adhesive).
skateboard grip tape?
Velco?
220 grit?
I take it you don't slide liners in and out every time you ski?
LOL, but hey, he solved the problem. I would've tried a rubberized paint ... I'm sure he will give us a chemistry lesson to why he didn't.220 grit?