It seems as if no matter where I position my holster, the size pants I wear, or the tightness of my belt, I always have a problem with IWB carry. I started out with an EliteIWB holster. Very standard nylon holster. Decided to get something with better quality, so ended up with an AlienGear IWB holster.
I carry a Ruger SR9c. Regular pant waist size is a size 32 but I can fit snug into a 31. I have a tall/slim but muscular build. Even when I'm WALKING, the holster doesn't feel tight against me at all. I'm very self conscious about it not being secure on me. I've actually had my gun fall out of my EliteIWB holster when I was getting out of my car once. Thank god no one was around..that would be weird. Maybe because it was a cheap holster? Maybe it caught on something? I don't know…but that was the last ****ing time I ever used that holster. Needless to say, I was pissed off and embarassed at MYSELF because of that incident even with no one to witness it. I've always worn a belt with my pants, too. I can't seem to find any solution to where it will feel tight and secure against me without having my belt/pants so god dam tight it hurts.
As others have said, a gun belt is a must for most guns. I've carried IWB at 4 o'clock for 20 years and have never found the perfect combination of gun, belt, and holster that I could carry with comfort. Even a Mitch Rosen holster and belt with a Kahr K9 didn't really work well for me.
I finally found the perfect set up that allows me to carry all day long in perfect comfort. I bought a lighter gun (Kahr pm9) and appendix carry in a kydex holster. This works so well that I don't even need a decent gun belt. I think the problem for me is that my body doesn't work well for IWB at 4 o'clock, regardless of the set up.