I had a Manton percussion double some time ago that mustve been stored in a very hot dry attic for most of its retirement, I could see the shrinkage in the wood from across the room. I purchased it, took it home gave the wood an acetone bath and a Tru-Oil refinish and some of the shrinkage did go away, but not all. I only freshened it up and didnt try to really restore it. As it was, I used it for preserve p-burd hunting and at SXS events. It was a 9/10 gauge that had been honed out to an 8.5/9 gauge.
Steve
