I bought the ATI Stoeger P350 Talon Adjustable Stock. With minor modification I was able to fit it on my Supernova.
Although, ATI told me that it "will not fit it with any modification." IT LOOKS GREAT!!!
Stoeger P350 Talon T2 Six Position Adjustable Shotgun Stock with Scorpion Recoil System
To start with,the Stoeger and Benelli are very similar in shape at the end of the reciever, with the biggest difference being the shape of the trigger guard. And that difference is not much at all. Listen, we all know that the "recoil spring rod" (on the Supernova standard) is a dummy rod, so you remove it from the reciever and your left with a hole about .300 deep in the reciever that is threaded. Now I emailed bennelli support and asked what size the thread was, but I recieved no response. It is M21x1. I guess if you can fin a M21x1. bolt, you could cut off .290 of it and drill and tap the center of it M12x1. but I didn'feel like looking and wanted to make the necessary mods myself to show that it could be done. So I made a threaded aluminum plug about .290 long with a threaded hole in the center to match the flathead bolt that is supplied with the ATI stock. bolt that is supplied is M12x1., not M8x1.25 as is stated in the installation instructions.Now the only other issue is the trigger guard. The pistol grip fits around the trigger guard, there's just not quite enough clearance depthwise. Break out the Dremel and clear it out a little deeper (if you do get this stock, as soon as you try to fit it you will see what I mean, IT'S NOT THAT COMPLICATATED. The mounting adapter sticks out a tad around the reciever, nothing a belt sander or dremel sanding drum can't alleviate. This adapter is what is called " hardcoated", but the hardcoat is not that thick. That being done, I taped off the reciever side and the stock side of the adapter and spayed it with Duplicoler spray bedliner to cover the areas where I sanded and also to make it more wear and chip resistant. Finally, I cut out a thin piece of rubber the same shape as the end of the reciever. this goes between the adapter and the reciever to increase the fit and maybe absorb a little recoil. THIS IS WHAT I DID, you dont HAVE to do it this way, once you see it you will see that there are other possibilities. MUCH cheaper than the alternative!