Having 2 ways to proceed, I felt confident I could always fall back on Allen's easier/lengthier method (fill peephole and re-drill) in case I didn't succeed with Tom's take-apart M.O.

Off I went with the latter and it worked like a charm ! BTW, you really have to be informed about the "tap left and lift off" in order to remove the upper half of the slide

Thanks again to both of you.