AA,
I guess I'm confused. You said that, as a long cure epoxy, it never really gets hard or brittle. I took that to mean Etex, which is a decoupage epoxy and does stay flexible.
D2T is, first and foremost, a glue. It does get hard and brittle, but, as a glue, you don't want it to stay flexible, or you would get creep, and eventual failure of the glue joint.
When I've used D2T to coat larger lures it has cracked and flaked when I did a rock test, intentionally of course. Hahaha
That was what got me onto Etex in the first place, because it dents but doesn't crack on the same kind of rock test.
I am totally lost when it comes to anything archery-related, so I will gladly yield to your expertise on anything that has to do with archery.