There's a tool for that.
Hey Stalwart. I kinda did this wit small plastic scraps. I balanced everything on the intersection of the point of all 4 contacts with the road (The tires). It was really tricky. Also, knowing that the weight distribution changes when the shocks come into play, doesn't that make the balance of the car off anyway?
1. check weight balance by balancing the car on a tool like the one here
2. then check the ride height
3. then adjust droop
4. then balance on the scales with the coil tensioners ONLY BY TIGHTENING THEM (because releasing tension will only take the pressure off the springs and onto the droop) screws.