Thank you, I will.

I think many people deal with this issue, and it's good to have a sharing of experiences. My own experience is that it is likely me, not my bike that is the problem. I had a Trek pilot 1.2 that was a little small (58cm) and am now on a 60cm Trek 520 that is a better size. the bars on both are about the same level relative to saddle. The distance from saddle to bars is a bit longer, but not radically. New back pain is likely due to enthusiastic effort, riding up hills with heavy panniers (grocery), and other things that I didn't do with previous bike.

I'm going to be attentive to the suggestions made, and do my exercises. Will report back. Stuck in hotel in Portland all week, and hoping it's clear and dry when I get home.