Don't knock it until you try it; few years ago I wanted to fist my wife, and she told me fuck no unless I let her fist me too. Dunno about up to the shoulder, but I can take her to the elbow with few minutes of working it in. Not all the time, since I, and she too for that matter, are pretty wrung out after such session, but once in a month, yeah. These stretching fantasies are pretty awesome to drive ourselves up for hard sex, let me tell ya xD