Another tip. When you've shortened the stock, get a length of plumber's PVC pipe of a width sufficient to fit over the stock bolt head. Insert it so that the bolt head is covered, and the pipe extends out the back of the stock. Now take one of those cans of spray foam filling material/insulation that you buy at the hardware store to fill gaps in drywall, etc., and fill the interior of the stock with the foam. Let it bubble out the back - you can trim it when it's dry. Allow it to dry, and either leave the PVC pipe in the stock (cutting it off at the appropriate length) or withdraw it, leaving a channel in the foam so that you can get at the stock bolt head when necessary. Trim the dry foam flush with the end of the stock (or slightly below it, if desired). You can now mount a recoil pad onto the foam, giving a better purchase for the pad screws. (If you want to, you can insert a couple of wood blocks into the foam at the appropriate places for the pad screws, and let the foam harden around them. A couple of projecting items such as screw or nail heads in the wood helps the foam to keep a good tight hold of the blocks.)
