[ILLusion]

grind off the nub on the bottom of the sight.

This is a common issue with PGC Hi-Capa slides.

Shooter's Design slides are a drop-in fit and require minimal work.

You'll also need to do some fiddling to press the slide down onto the rails while tightening the bolt which holds the blowback chamber in place. You'll need to find that "sweet spot" where you get maximum torque of that screw without screwing up the slide movement.

Alternatively, you can find the offending locations of the slide that force the blowback chamber to protrude and grind those off as well.