Nice shotty you have there. That's a perfect platform to start your own tactical shotgun if you'd like. I have the same one except it has an 18" barrel on it. I put a Knoxx SpecOps stock on mine to reduce recoil, and to save my shoulder from getting bruised. I may put a sling on it too, but nothing more.
Also later, if you want to install a mag extension, it would require drilling out some indentations that were made at the factory to prevent a mag extension from being installed. Anyway, have fun with your new shotgun, I know I have fun with mine LOL!!!!!!!