Hap,
You are exactly right as I have learned this afternoon while fletching a dozen arrows for the Colorado Traditional Archers Society shoot next weekend. The 'L' shaped lip faces down when using the wrong wing chopper. It works but, it makes it harder to hold the feather in place and get a good consistent chop. After this, I will either buy a right wing chopper or use my burner for RW feathers. BTW, I do use my LW Bitzenberger clamp and index with a RW clamp and do just fine glueing feathers.
Mike