Here's an interesting data point. I measured my body height when my truck was fairly new ... 40.25" DF, 42.375" DR. Now with nearly 40k miles, I measured again. The rear has sagged almost two inches, to 40.5". But the front has also sagged, to 39.5". That was a surprise. I had been thinking that the truck was looking lower to the ground than before, but I figured it was my imagination. Both measurements were made with an empty truck, 38psi all around. But I had a half tank before and am nearly full now. I need to remember to re-measure at a half tank, but it seems a bit unlikely that a half tank of gas will drop the rear by almost two inches ....