Trophy Stock suspension Question?

[RL Wiltshire]

The rules read that the car can not be lowered more than 1 1/2 inches. I am reworking my entire suspension and need to know the best way to tell how low is too low? Where is the measurement taken and what is the lowest allowed height at that point. My suspension is killing my et's and most of it is gonna get replaced.
George, Hope you don't mind answering these questions on the BBS, but i thought maybe if others had the same question it might save you and others some time?
Randy
T/S 34
12.52 @111