[zauber1]

In reply to the original question: As one of the only two shoulder rig supporters, here are my antiquated reasons for this means of carry:
I carry while wearing a suit and/or sports jacket OR in the oppressive heat and humidity of the Dallas/Ft Worth area, a really loud print, oversize aloha shirt with the tail untucked. I am frequently in and out of law firms and downtown Dallas offices in my capacity as a law enforcement officer and need to pass unheeded.
Remember the oldest detective Fish in the TV show, Barney Miller? He was frequently in the restroom a lot (like me) and, you guessed it, wore a shoulder holster. Ever gone into a public restroom and looked for a convenient and safe place to place your weapon while doing your business?
I also find the shoulder rig balances out the extra magazines and cuffs on the other side without pulling down my waistline.