Skirmished with it at Wasaga today.
I found that if I don't put the retaining nut on the magwell pin, it feeds fine. I actually didn't have a single misfeed all day. Of course, this isn't a perminant solution (although the pin is friction fit enough so it shouldn't be an issue), but seems to work for now.
I'm not sure if the problem is that the hole on the magwell is off spec, or my pin is off centre, or what. All I know is that if I put the retaining nut on it moves the magwell about 0.5mm, which causes it to stop feeding.
"Someone in a Prius tried to race me at a stop sign the other day. I couldn't believe it. I had him for the first 100 feet or so but I can only walk so fast."