The way you remove screws that have been set in epoxy is to use a soldering iron held against the head of the screw to heat the screw up and soften the epoxy holding the threads. Then once it's hot, you remove the screw with a screwdriver. However, as mentioned, punching holes in a stripper's skin near the waterline is not to be taken lightly and carries a certain amount of long-term leakage risk.
Rather than mechanical attachment of metal bands, I finally settled on adding a tiny strip of Kevlar felt, directly on the spots of the lower stems where abrasion happens. Kevlar felt is the same stuff that Old Town and other companies use for the Kevlar skid plates on their Royalex canoes. It pretty much stops the abrasion issue dead in its tracks. It's not the most beautiful stuff in the world (dull gold color, but can be painted over if desired) so you want to keep the sizes of the pieces to a minimum and apply it carefully. The best thing to do is to use the boat a bit and find out exactly where the abrasion usually happens. It's quite often concentrated on a very small area, depending on the stem profiles. Sure, you might occasionally hit a rock with the surrounding, non-felted area, but the glass can probably handle that. You're interested in covering those small areas that get abrasion on a regular basis.
Once the trouble spot is located, it may be small enough that you can cover it with a piece of the felt that's only a few inches long and 1/2" wide or less. We found that we could stop about 95% of the typical stem abrasion from beaching (assuming reasonably careful boat use) with a cigar-shaped piece of felt that was about 4"-5" long and only about 3/8" wide. Application is a matter of removing the varnish in that area, saturating the felt with epoxy and sticking it on. Neatness counts, because you can't sand Kevlar felt (it just gets fuzzy on the surface and that's as far down into it as you will get). If you decide to go with it, we can get into neat application tips when you're ready to install it.
The felt is style #4580 and can be found here. Not cheap, but a half yard would do a whole fleet of strippers.
http://sweetcomposites.com/Kevlar.html
For repair of general bottom scratches on strippers you can cosmetically hide many of them with nothing more than a coat of varnish. Anything that's really deep can be epoxy-filled and sanded smooth first. I usually do occasional varnish touch-ups and then every few years, I'll sand the varnish off the bottom, epoxy-fill any bad scratches that are left and re-varnish. Re-varnishing should be done periodically to renew the UV absorbers and protect the epoxy anyway, so you can kill two birds with one stone.