MOD1 did the work on both of my Carry Optics Glock 34s, and I couldn't be happier.
They specialize in Glocks and M&Ps, but will work on other brands as well. Prices are very competitive and the owner/gunsmith is a perfectionist.
Not sure what kind of optic you plan to mount, but he has a proprietary method of getting the RMRs as low as possible with BU irons, which helps with acquisition and sight tracking.
Personally, I shoot the Vortex Venom 3 MOA.
http://mod1firearms.com/