That is actually strobro32's (on this forum). He also posted pictures over at SilencerTalk. I asked him some questions about the rifle once you cut the stock, and it is essentially the same as the pistol once the stock is cut. He customed up a folding stock and it looks pretty good. Here are some pictures he sent me (and said I could post here).







So a plug for the hole in the rear of the receiver with a mount for the buffer tube is really my ultimate goal. There was a guy that made an adapter for the pistol at one point that should work on the rifle, but he seems to have dropped off the face of the earth. I wish someone else would pick up and make that adapter. Then I could use it, plus one of these 404 - Document Not Found and a buffer tube to get what I want.

Here's the video of the adapter piece the guy made:
Smith Wesson 15-22 pistol butt stock mod full auto - YouTube