[Unclenick]

There is so much variability in frame machining tolerances over all the available 1911's that I don't think I've never seen a mainspring housing that was very tight. All have been drop-in. Keep in mind the hammer strut bears down on the mainspring plunger (cap) even when the hammer is forward, so there is constant compression of the mainspring that keeps the housing pressed down against the assembly pin, and that keeps it from wiggling around.

The only fit issues I've encountered were with grip safeties having long feet that rubbed the mainspring housing, or that were too thick and stopped against the step at the top of the mainspring housing prematurely. These can be remedied with a file taken to those feet.

Before you change the arched housing, ask yourself if you are going to use this weapon in rapid presentation from a holster (quick draw). If not, you may like the smaller total grip frame reach. I do, and I use a flat mainspring housing on my 1911 target pistols. But when I put a flat mainspring housing on my combat gun, I found my hand was more likely to grip the pistol in not exactly the same place each time, when working at the speed of a rapid presentation. I switched back to the arched housing that tended to funnel the web between my thumb and index finger into the correct position up against the underside of the grip safety tail.

I'm not saying you'll have that exact same experience. Everyone's hands are shaped a bit differently, and some may slip into place better with a flat housing. It's just something to watch out for that not every possible modification turns out to be an improvement. The arched housing itself is actually a modification the army made to the Browning design. They also radiused the bottom of the slide pin stop to make slide racking easier, but that also increases muzzle flip by unlocking the slide sooner and giving it more velocity. It seems there are always tradeoffs. I always put long triggers in the bullseye guns, but in the combat gun a short trigger works better for me because of the speed and because I have that arched housing there.

I'd say the one grip frame area modification I like best and always use is to install a beavertail grip safety. That makes it easier for me to shoot a long session without the flesh behind the web between my thumb and index finger becoming red and sore by the end of the day.