Legal for Service pistol

Accuracy X system of an adapter plate that screws down to the slide with the adjustable rear sight drifted in to the top.

Legal ???

Are there any other options out there other than drifting out the rear sight and screwing down a rail to which I would clamp an Aimpoint H1 (and other than multiple slides.).

Contact CMP and ask them. Logically the pistol becomes “reconfigurable” from irons to optics. And if in “irons” configuration it should be OK.

Of course it’s legal!

Just easier than unscrewing your rib, reinstalling your front sight, reinstalling your rear sight. Reestablishing your zero at 50 yds.

Another option would be a frame mounted dot. The mount could be removed for service pistol and the iron sights would always be in place. That being said, I have an Accuracy X with the multi-sight setup and it's perfect.

It's so legal, at least 2 CMP national championships have been won with that exact pistol with that exact sight setup.  

https://accuracyx.com/accuracy-x-inc-1911-wins-national-championships/