I've got crushed discs, scoliosis, degenerative spinal disc, arthritis, and more I don't want to think about up and down my back. I OWB a Beretta 92FS in a Blackhawk Serpa and an XD(m) Compact 3.8 in a Galco Fletch. A really good gun belt makes all the difference for me for OWB. 50% of the time I carry each in a Galco Miami Classic shoulder rig, properly balanced of course. I decide what to carry and with what based on a lot of things but pain is a factor. If my lower back hurts worse, I use the Classics. If upper back is the bigger problem that day, it's OWB using a Blackhawk Instructor's gun belt.
“There are no stupid questions, only stupid people.”- Mr. Herbert Garrison
"Never underestimate the power of stupid people in large groups."- Jeff Cooper
"Those convinced against their will are of the same opinion still."- D. Carnegie