I agree with Randy, with a good belt and holster you shouldn't have any problems carrying your Kimber inside your waistband (IWB). Personally, I'm a big fan of CrossBreed belts and IWB holsters.
Yep. Belt makes a huge difference. For gun belts, I strongly suggest either getting a dedicated leather gun belt (multiple layers, stiff, extra stitches) or something like a Wilderness Tactical belt with the nylon insert (which is my preference).
If the belt is sagging, the belt isn't strong enough. Also, belt/pants fit when paired with the holster makes a difference.
Since you aren't a small guy, is there a reason you like the smaller guns? (For example, I'm not a big guy at all, and I carry a G17.) Larger guns, in general, are more stable than smaller guns. (And a Glock 23 has about the same weight as your Kimber.)
I'm thinking that lots of people like Crossbreeds (meaning it is normally a solid carry holster), so that paired with a solid stiff belt, it may end up working for you directly.