[Trevor Booth]

Another simple and accurate method in attached photos.
A note of caution. one degree of twist may permanently set a light chassis. A reliable method to establish applied load (L) Mass of vehicle with fuel oil and occupants(W)
L=W*0.25*wheel track (widest). I use a digital level and measure setup angle front and rear, apply load and measure deflected angle front and rear. Deduct set up angles front and rear and the difference is angle of rotation. To obtain torsional deflection at intermediate points use digital level or dial gauges(under chassis sides).