I have used 6moa vortex venom and viper red dots on pistols. I have had better luck with venoms. I own 3 venoms that work great. I had to send 2 vipers back for replacement. Also I shoot morning matches where we face eastward towards the sun. The viper screen would get a lot of red glare which would make finding the dot difficult. For whatever reason the venom doesn't do that. As for Primary Machine they cut a CZ pistol for me. It was for a venom . They did a quality job with a quick turn around.
In answer to the red dot question, my newest 1911 is an Arctic LW 9mm stainless that came With a Vortex Venom already mounted on the pistol. It fits well, and was super easy to sight in. It even fit perfectly in my Blackhawk Serpa, even with the red dot. So far very pleased.