There has been discussion about riding positions and various aches and pains. For those of you with bad backs, you might look into the Back-A-Line:
I purchased mine when I had my 1980 Honda CB900C with its bolt upright riding position. I would start slouching after a few miles and get a sore back. I have not needed it with my ST's, but those of you that are still experiencing back discomfort may want to try it. Bear in mind it is a support device, not a back protector.