Ok, so maybe I'll get a few folks riled up.
I've got a Mossy 500 Cruiser (JIC without the PVC container, I can make that). Mine came with a Blackhawk recoil pistol grip, and I've been very please with what it can do. I can actually aim mine for a little more accuracy (not as much as a shoulder stock) without busting my nose.
My buddy has one with the original grip, and yeah, it hurts to shoot it after a while.
But all in all, for what the JIC was designed for, I'd get the 500, put on a recoil reducing grip (if overall length is that important) and build a container.
I've got a Mossy 500 Cruiser (JIC without the PVC container, I can make that). Mine came with a Blackhawk recoil pistol grip, and I've been very please with what it can do. I can actually aim mine for a little more accuracy (not as much as a shoulder stock) without busting my nose.
My buddy has one with the original grip, and yeah, it hurts to shoot it after a while.
But all in all, for what the JIC was designed for, I'd get the 500, put on a recoil reducing grip (if overall length is that important) and build a container.