The before and after actual head clearances are something that I didn't do unfortunately. I am 6'3" and my head hit the headliner so I had to scoot forward in my seat away from the lumbar area and slouch to clear the headliner. I was having horrible back pain and couldn't stand to drive it for longer than my 45 minute commute to work. After lowering the backof the seat by 1-1 1/2" not only do I have just the right amount of head room now but my back stopped hurting since I didn't have to slouch. Amazing the 2 benefits out of this1 fairly simple mod.