I'm no MD or chiropractor but to me, the small of the back is the area above your waist or tailbone where the spine begins to curve.
Not on the sides or hips.
FWIW, Blackhawk,
www.Blackhawk.com sells a line of decent black leather holsters angled to fit in the rear hip area. The description states it allows the wearer to access the sidearm & avoid problems with a long gun or SMG.