It's been my experience over 30+ years of carrying that if your holster rides too high, the butt tends to pop out. This is especially true with shorter barrel pistols. For the G23 I carry every day I like the Galco Concealment holster and Milt Sparks 55BN. The sparks doesn't hold quite as close to the body as the Galco but it is one of the most comfortable designs I've ever used.
Certified Glock Armorer