Wow, that shotgun is teh secks...
Darn it, I'd originally written off that stock due to the cost and the regular folder is starting to grow on me. Seeing that beast is making me seriously reconsider... (but $258+98USD?! my wallet is crying over the other projects I'm running) Is the rail that comes pre-attached to the stock/grip removable? I may go for an ATI heatshield with ghost ring sights and the rail would probably get in the way of using those.
Wait, I just found
this. It looks to be gas compatible (and it's in the buffer tube too, see the hose coming out?) and it's a hell of a lot cheaper than the one on redwolf. It looks closer to the one on the shotty there too - more squared over the smoth rounded PM one.
Also, a quick trip to a local gun store and I found a bunch of mag extensions, as well as the pistol grip fore-ends. I'm hoping that the conversion process from real to airsoft isn't too complicated.