In my previous post, I forgot to mention the name of the adjustable stem that has done a lot for my lower back. The brand name is Kalloy, and it sells for $20-25. My local Trek dealer had it in stock. He charged me $5 to put it on. My handlebar is now 3-4 inches higher than it would be with a standard, non-adjustable stem, and it's still not all the way up. But when I feel "racey," I can lower the handlebar to its standard stem position with just a turn of an allen bolt. The unit is made out of some kind of alloy -- it's light and won't rust. I haven't noticed any additional wind drag due to my more upright position, but I'm really not a fast rider. For me, a 15 mph average for one hour over hilly roads is a major accomplishment!

thanks for the follow-up! am now taking a look around for these things; I'm amazed I hadn't seen them yet.

--alex.