Well, what do you do when you cannot rig up a torsion test? Why you skip the test and overbuild of course!
To do a torsion test properly would have required 400 lb weights (or heavier) and a strong garage floor to which the rear of the chassis could be bolted. Alas, we have neither. So, we opted to add cross bracing to the chassis, skip the torsion test, and hope for the best. Opinions on what we did are welcome.
So, we added cross-braces to the chassis between the suspension mounts. These we made out of 3/4″ x 0.062 wall square tubing. I welded these to all of the tubes and cross members. And here are the results:
Frame with x-braces installed.
Close up of cross-bracing