What I've found over the years is that once you're reasonably proficient with a weapon, you no longer consciously "build the castle," though I suppose that it still occurs. Every really proficient shooter I've ever spoken to and shot with all agree that you focus on the front site, with the target somewhat out of focus, and pretty much ignore the rear site. I'm not really expressing this very well, but it worked for me in both 50' small-bore rifle and handgun competition. In the case of the rifle competition, using an aperture rear sight, the sight was forgotten altogether.
Once in a USPSA handgun competition, after the first shot, I noticed that something had changed, but was able to complete the course. It was only when I was clearing my handgun that I noticed that the pin holding the rear sight on my pistol had come out, and the rear sight completely fallen off the gun. While my score on that round was somewhat lower than the other rounds, I was still able to shoot fairly accurately (for practical shooting) without a rear sight.
Having been unwittingly caught up in a gang-banger, dual-pistol execution field-of-fire (New Orleans, 2006), I can tell you that there are so many bullets, pieces of brick, cars, and everything else flying around, the shooter is bound to hit something. I was flat on the ground. My partner got part of a round in the top of the skull, but he’s a marine, so it didn’t hurt much. There were two others wounded, one fatality. These guys don’t aim, and they don’t get usually get caught, either. They don’t expect to live long, and they most interested in speed and volume.
Not a hand gun shooter, but wonder if holding it like that would interfere with ejection of spent shells.