Thanks for the tip T7..........

That rubber I mentioned pours in just like goo. It fills just about every nook & cranny, and it dries in about two or three days. It's a very dense rubber like an old super ball and provides considerable weight. Both the rubber itself, and the extra weight of it, would reduce felt recoil by quite a bit.
I've got the Great Stuff and after I pull the gun apart, I'll check it all out.
Got to shoot her first though........

Thanks for the suggestion.

Bob