When duct tape is just not what your looking for..... I bring out the camo Ratchet Straps.
I now use two ratchet straps on my shotgun when using my adapted brace. One to hold down the rear stock and another around the butt plate to eliminate recoil. I add a plastic wire tie to the barrel and my shotgun doesn't move much when I shoot.
My accuracy has gone up 200 %. I will post some pictures of it all soon