I wouldn't worry about a sand-thru on the top. It is already rustic with the ski wear and tear. It wouldn't be that big a deal, so don't let it mess with yer head. My only suggestion, and you may have done it and just not posted it, would be to take a piece of ski and test your finish on it. No telling what was on the ski to start with, and it's always a good idea to see how your finish is going to work, compatibility-wise. That being said, you can always shellac in between the two to make sure. Your build is looking awesome. Unique, imaginative and well executed.