I carry a commander-size all steel 1911 most days. IWB, about 4:30. Two spare 8 round mags owb at 7:30. A flashlight at 10:00 and a knife at 3:00. On a Wilderness instructor belt, all covered up by an untucked shirt. I'm not particularly heavy, but I'm certainly not rail thin, either. I'm perfectly comfortable. Once in awhile I need to just nudge the gun a bit in one direction or the other on the belt to stop it from digging somewhere. But generally it does just fine.
However, I had to cut a couple of new holes in the holster and move the belt loops down lower on it, to make the pistol ride a little higher than it otherwise would have. I also added a bit of additional cant to it. In its factory configuration, that holster caused me some pretty serious discomfort, no matter where on my beltline I put the pistol. So if you find a holster/gun/belt combination uncomfortable, just experiment with it until you find out how to make it work, and be creative in your thinking.
Some days, when printing might present a particular problem for various reasons, I carry a small 380 iwb with a couple spare mags and I can honestly say I have to occasionally remind myself it's there, because I could easily forget all about it. With the little gun, I don't even need a real gun belt. I'll carry this wearing a cheap little dress belt or whatever.