I don't have the luxury of a frame machine or even a lift, and back problems limit what I can do compared to a "normal" person. I figured my garage floor slab is pretty flat, so I can reference all my dimensions from that. My problem was finding a "known straight part of the car" to actually put a level on from front to back. The frame rail, lower rocker, window sill, trunk floor, floor pan, etc are all at different "inclinations". I ended up using the door sill as it seems to be the best compromise between all the other points I've tried. Since my stands are under these torque boxes, I think I'll measure the heights of the stands just to see how close they are. BTW, that rotisserie was built by a mechanical engineer. I got it for $300 after he finished using it. The smallest material used is 1/4" and the connecting tubes are 1 1/2" pipe (I had to lengthen them with some 1" pipe inserts). Much better than using a pair of HF engine stands as I've seen some on here do...