Need Suspension Help
 

I'm trying to figure out if the rear springs on my 97 2wd 4.6 are sagging. I know that the rear should be 2" higher than the front. However, when I measure from the ground to the high point of the wheel well on level ground the rear is only 1" higher than the front. Does anybody know if it should be 2" higher at the wheel wells or a better way to tell if the springs are sagging. The real problem is that when I tow the rear almost bottoms out. The trailer has less than 500lbs. tongue weight so it should be able to handle it. Any help would be appreciated.