Mickey,
As "Butler", said a lot of old-timers used to make a dummy to fit in the cutoff mortice. Yeah, I am an old timer, now, but I always used a piece of steel drill rod instead of brass. On one of my rifles, I used a spare real cutoff and just filed a flat as a clearance for the hook on the sight base. I did that just in case I ever decide to shoot under "CMP Rules", I could just remove the sight and not have to futz with re-installing the cutoff (after FINDING it, of course!) I'm sure they would insist that a cut-off be present. They might even put up a fuss about the small "modification" of it. If so, I think I'd just tell them where to go. I have achieved Curmudgeon status.
Respectfully,
Bob S.
Resp'y,
Bob S.
USN Distinguished Marksman No. O-067