Drivetrain Checking for bent rear end

I think I figured out how to check if an 8.8” rear is bent without the housing end tool @CarMichael Angelo borrowed from a friend.
Before I tie in the algebra I have been helping my kids with, which tube or tubes is most likely to bend and are they going to twist or move forward or back?

A hint, they have been graphing parallel lines and linear equations. All I need is a straight edge and a caliper. And no more freakin’ snow with daily highs below zero.