ill have to try the towel thing. i find that my cars lumbar support feels like its more like over extension. a towel mid back would probably help me out. for shoulders i tend to use the steering wheel as a form “bend the bar” to promote external rotation. once thing that really bothers me while driving long distance is my ankles/heel. especially the one i use for the gas pedal. no idea how to help that out… i find that when i drive with base feet its a little better then with shoes. but other then that not much has helped.