I've already tried the S&J Hardware +1 for the 590 and it did not actually let me get an extra round in the tube. The Suarez unit is supposed too have been specifically made for the Shockwave and actually add a round. But it's no longer p\on their website. They seem to be heavily invested in the Tac-14, so they may have stopped making the Mossberg +1. So has anyone added a +1 to your Shockwave that works? Which one?