Boat = Inter 20

I am going to be upgrading to the new mast base that will render these holes obsolete and figured while I have some West Epoxy mixed up for some other stuff I would fill these in. Problem is it is just far enough up in the mast I can't reach it to put a backing to dam the epoxy.

Any ideas? I was thinking of clamping an old batten in place with either covering it with wax paper to keep it from sticking/bonding or a partial cut to break off once it is sets up.

Has anyone done this repair? Or have any other recommendations?