I've got a 1911 whose new grip safety, after being fitted, refuses to move out of the 'engaged' postion, that is, it won't move back to allow the grip safety to actually function. After applying inletting black to just about everything to find out where its binding, I'm still at a bit of a loss. Any thoughts as to what might be hanging it up and preventing it from functioning?

I would bet it's either on the bottom (just above the MSH) or on the sides of the arm that block the trigger bow or the hole for the thumb safety pivot is too tight. The inletting black should lead you to the problem. Was the frame of the gun ground down to fit this part (not a drop in)?

Is it free or is it in a hard bind?

Remove the MSH pin and let the housing drop about a 64th of an inch to see if it resets.

If it's free and loose, it may be that the underside of lug is contacting the top of the trigger stirrup and keeping it from resetting.

Simpler than I thought. The sides of the grip safety were simply a few thou too wide for the frame. The one part I didn't think was binding. Go figure.