This is not a go idea . It will make the hub twist when appyling the brakes and start breaking the spokes . Just by hub adapters . And also mounting a rear gear them same way will damage the spokes . Believe me I try the same thing on the front of a occ chopper
Vance if it's concentric how is it any different than a disk hub? that doesn't twist the hub or break spokes unless the spokes were not at the proper tension to allow the hub to shift!