The Perry instructions recommend drilling through the mounting flange as an option. If I were using a regular pressure nipple, I would just drill through a flat area on the backplate and make sure it doesn't stick out into the crankcase.

Tripacer, you got it!

Joebob, if the engine runs fine with just a check valve for a couple minutes, then it probably will be fine, 'cept for the fuel spewing out when you shut down. I think rich runs are inevitable though.