Don't let making a bead of thicked epoxy scare you off - it's an easy job. Get it good and thick so it stands on its own, and use a spatula of whatever sort(I've got a collection of gift cards I save up) to make a mountain of it along the seam. It doesn't take much of a jig - it doesn't need to extend beyond the panels at any point. Just run your spatula along the panel on either side to create a sharp edge - an epoxy extension of the outside of the panels. Once it's set, a little work with a rasp and sander makes a nice smooth radius for the glass.

Filled epoxy is a fair bit tougher than the ply - and this is a good spot for impact protection. Ask the guy who ran his boat headlong into a piece of I-beam that some helpful sort had cut off right at the water's surface. Maiden voyage, no less. The bead showed a scratch, nothing more. The wood behind it had a minor (less than dime-size) delamination. A wood bow would have suffered more, tho probably still only cosmetic damage.