Raimey,
you caught me. That's the 12g BSS that I used for comparison. The pic below is the 20g. The parts still look different, but the sharpness of the 12g parts caused me to look over the 20g parts closely. I did the work without disassembly since you can just pull the inertia weight back and gain access to the faces of the parts. You can see the wider flat on the rear part where the tinkerer took material off or it was just fitting by the factory. Either way, it drew me to look at the corners for rounding. Found it, fixed it in 10 mins.
