Measuring the flex in a 928 chassis
 

Any ideas on some kind of simple test to measure the flex in a 928 chassis?

I am curious about how different model years and mileages would compare.

Isolating the effect of tires and suspension would be essential, so I am thinking the whole car would need to be lifted by some points on the chassis until the tires clear the floor, then maybe raise one corner some fixed amount and look at the height change on the other points.

High spring rates will show up the flex in a 928. You won't feel it, but they can creak a little.