Hmmmm. Is that clamp the smallest size they have? You did say you added that didn't you?

At any rate, I've never been clear where you are wanting to epoxy the shim. Seat post, inside seat tube, outside seat tube, or maybe inside clamp.

Outside seat tube or post seems easiest to me. As well easiest to remove and change if later condition warrant.

Still, it seem a toss up whether or not you should epoxy it on. Just more what make you feel better.