Like you. 2011 frontier and now ridgeline. I thought the frontier seats were great but I find the ridgeline even better. My wifes 2011 Highlander were way to firm. Would get road weary after about an hour. Owned an Oldsmobile Aurora for a short time that couldn't stand to drive over forty miles. My back would be killing me. Sounds like you need to get your back checked out by a neurologist. You might check this out. I have one which causes me some lower back discomfort. Synovial Cyst in the Lumbar Spine They are pretty common.