Very interesting videos. I have to agree, though, that if I were to go to the trouble to make a complete video set up like that, I would explore making a wooden mount for the action out of a 2-by-4 or something other than an custom walnut stock. After all, if you're going to aim with a video camera and shoot off a tripod, you don't really need much of a stock in the conventional sense. Maybe rig a camera cable release to fire the trigger as well.
Anyway, pretty amazing videos.