As most probably know, Sig has released a P229 long extractor slide that is also drilled for the RMR bolt pattern.

My slide arrived yesterday, so I though I would add my comments/observations.

Fit and finish is as expected.
Cuts look less crappy in person than they appear in the photos, but your opinion may vary.

I compared some weights between 2 P229 long extractor slides.

First (2015 vintage) assembled slide (less barrel and recoil spring assembly):
11.5 oz.
New slide weighs 10.0 oz without the cover plate and 11.0 oz with plate.
New slide weighs 11.5 oz with a Holosun 507c mounted up.

Based on the weights above, I would expect reliable performance with or without an optic mounted.

The stock 8/8 x-ray sights will be to short to be seen through the optic glass.

I have ordered some Dawson Precision all black (no dots or glowy things) in the .250 height area. Based on my dial calipers, they should just barely sneak into view as an super low co-witness.

If I’m wrong about that, I’ll fix it and report back with better size recommendations.

Sorry if this is a dumb question, is your post about what is called the "PRO-Cut" slide?

I believe that is what they are calling it. I would have preferred a stock slide, but that option doesn’t exist (with an RMR cut) from Sig.