The answer from the IDPA is (from Dru Robbins) -
You can put iron sights on your gun and shoot it in IDPA. If you slide
were
skeletonized, you wouldn't be able to use it, but if you're just
removing
optical sights, that's fine. As long as the gun fits division criteria
and
the purpose and principles of IDPA, go for it.
So it looks like I'm set to go ...
Thanks again for everyones reponses,
Victor6