I agree! I have a foot rest, but I sit with my leg crossed, one foot on the footrest. NOT good!
Also -- I was going thru physical therapy in 2001. My back was hurting and no meds were helping. DH (boyfriend at the time and hadn't been in my car much) and I drove to Reno and back. He said HIS back was hurting. We'd used my Caravan. I decided I'd trade it in and see what happens. NEVER had another lower back problem after I got rid of the Caravan!! Now, to really understand how something can botther your back, I was driving only 10 minutes to work and back every day and occasionally long distance.