The last 4 years on the job as a Detective in a big city, I carried (in condition one of course) either my Colt GM or Colt Defender Plus. Both fit perfectly in my Bianchi "Carrylock" Model 82 Colt Officer (belt) holster. I was a working cop, search warrants, arrests, hot stops, etc. in one of the city's busiest divisions. Almost everyday in the field, in & out of both plain cars & black & whites. Involved in numerous physical confrontations on the ground (asphalt), foot chases, jumping over fences, etc. Never a problem with the holster.
The gun stayed secure until I wanted it. Never came out unplanned. Easy to draw (with practice) and easy to one hand re holster without looking at the holster. As you well know, the 1911 requires more vigilance than a standard DA/SA platform. I developed a habit of checking my safety frequently, making sure it was engaged.
The holster rode close to my body (suite & tie) and stayed put. Holsters like guns, are very personal, especially when you carry them for a living. Take your time, find one take just right for you. I highly recommend the Bianchi. I paid it the highest compliment. I bet my life on it!