Just bought an "optics ready" P220 Legion .45 and am looking for advice/suggestions/choices on red (or green) dot optics that are most compatible for carry. Another forum thread suggested Romeo 1 Pro. Any others?

I would spend a little more for a RomeoX. It's a more rugged red dot that is also small enough that you won't have to replace your Xray3 Night Sights with suppressor sights to co witness. Just make sure you don't get the Compact. It won't fit.

Agree with DanH. My Romeo 1 Pro has been decent, but it has had a few issues, to the point where they are working on RMAing it for me. Sig CS has been great, and the optic isn't horrible, but it's had a couple of uncommanded zero shifts and failures to wake from the motac sleep mode (like 2 or 3 times in a year and a half of daily use). If I could do it all over, I'd rather have the RomeoX (although to be fair that wasn't an option when we got the Romeo 1 Pros) if only for the ability to keep the standard height sights. The build quality also appears more robust, it has better buttons, and there's no need for the metal shroud which has a nasty habit of smacking my thumb when I shoot one-handed. I haven't actually gotten to use one yet, though, so I can't say if it would actually correct the issues I've had with the 1Pro.

I just sent a P226 slide out last week to get milled and opted to go with a Holosun 407k on that one. IMO if I'm spending my own money on it, the Holosun is a better value for the money, and possibly a better optic overall. From what I can tell without actually being able to mount it, the 407k is small enough to not extend past the edges of the slide, which was appealing. I'm still waiting to get the slide back, though, so I can't really speak yet to how that setup works out.

I put the Romeo X on my P220 Legion and love it