I've done it, but I also bent the buttcap and edge holding it in. You might be able to salvage the cap (plate), but you probably won't be able to restore the edge to it's original look; it's just thin brass bent over to hold the cap in place.
If it were me doing this, I would knock the cap out, clean up the edge as best I could and have Strydur turn down an MPS#1 to fit the ID of the graflex tube (1.39"ish). Then it's possible to use any MPI, and there's a 1.25" ID at the pommel for a chassis or speaker can.