Originally Posted by Precision1

That measurement is usually shock length (from center of fastener to center of fastenere). But to match this you need to have the shock in the same position on arm and tower.

Better way is to have it on set up blocks with wheels off and measure distance under hubs to ground. You can find the max droop this way and adjust for different shock mount positions on arm so shocks never fully extend when in the air. You want the droop screw to limit travel before shock is at max extension. Otherwise you will destroy shocks pretty quick.

If you don't like the Tekno way of adjusting droop from the bottom, get some of these.

Ball bearing droop screws
A little pricey, but so is a $600 truggy!
They work great, I have them in everything. No more chassis gouging or unreliable droop settings.