gcp,
I'm gonna disagree with the chain idea. I also disagree with the need for flexibitlity on a 2 point hitch type mower. If you want the mower to follow the contour of the ground, then you have to use a "Pull" type mower. It will either have wheels at all four corners, and/or attach it to your draw bar. It's pulled like a trailer, not a 3point hitch.
The scalping is because you didn't lift and adjust the cutter as you mowed. This is operator error and has nothing to do with adding chains.
I'm not sure where the chain idea came from, but have a pretty good guess it's from older tractors with very minimal strength in there lift arms. Older tractors just didn't have very good hydraulics. Especialy in the smaller models.
Chains will only help support your lift arms and take off some of the weight. There is nothing else that they will do. If your arms are droping from the weight of the mower, then adding chains will stop that.
They will accomplish nothing towards scalping. You will still have to adjust the mower as you operate it.
Congratulations on a great deal!!!
Eddie