Modded using the stock motors and a 9.6v NiMH battery, so thought I'd get a more middling crush level to keep from overwhelming the motors; I settled on the 42mm cage, and I regret it. It seems to shoot nice enough (though I don't have a crono for hard numbers), but after running a bunch of mags through, only the outside of the wheels have any dart debris on them. It looks like the darts don't touch the inside of the wheels.
If I were to do it again I'd pick 41.5mm or less to see if I can't get the wheels to fully contact the darts.
That said, I loved everything else about these, so I see a smaller size in my (near) future.