I don't use it any more but many years ago when I was a tot and keen
shooter, this was an age when shooting was a normal and natural pastime, I
built a shoulder grip not unlike a rifle butt. Using a lite 1/2 by 1/8th
flat shoulder curve bronzed onto 1/2 tubing with a bracket along the tube to
mount the camera via it's tripod mount with a pistol grip at a suitable
distance from the shoulder against which the end of the shutter release
cable was mounted.

Your question does it work. Sure did. Never the less as I became more, let's
say, precise seeking I opted to use a tripod. This contraption needs a rifle
users technique to gain maximum advantage. I would recon it to be about as
efficient as a monopod.  One can buy these things from time to time.