I finally sucked it up and bought one. Brownells has them in stock and active junky gave me 7% back.
I stopped by the range and "mag dumped" it twice. With an unloaded shotgun I'd load untill full. Shoot untill empty, then repeat.
I did it with my shockwave once, then my stocked 590a1. I think it's a good addition to a side saddle and the shockwave where I don't want to make it heavier. The micro rig is a nice way to add some extra rounds.
Trying to load the shockwave from the chest puts all the weight and torque on your right hand. Make sure you eat your Wheaties. It's doable, but noticable after a while.