Going from a 16 in to a 20 in should net you about 100-150 fps depending on which round you go with. If you like the look and feel of the the 20 in A2, then go with that. Although you may wind up having to build your own. I know that Stag has the model 7 which is a 20 inch model, but its not in an A2 configuration. As for RRA, most owners speak highly of them here on the boards!