Jake, since your looking to replace the inside I'm going to assume you know how to or have taken it apart. This is something I have done and it works. Get some epoxy (laminating works well) put a little mill fiber in and use a small foam or regular brush and paint a thin coat on the high side of the stick. Let it kick then do it again. It helps if you put a little on the inside of outer stick. Let it sit for a week then sand and feather the edge. Finish sand with 400 wet and dry. As you sand check the fit from time to time. You'll be able to see where you need to sand or add. I do touch-up paint work for car dealers so another thing I'll do is carry the stick with me and when I have left over clearcoat I'll put a couple coats on,let it sit then add some more etc. Gel coat sprayed with a preval or brushed on would work too.

Have Fun
Mike