Comp Engineering Frame Ties Install Question

Quick poll here- I’m installing the comp engineering frame times- bolt/tack welding them on my Duster

Now my question- their use instructions say to let rear hang and jack up the frame, I’ve always been under the impression you want to avoid sagging and load suspension like it would be on the ground? I’m leaning towards using my tire cribs under 4 tires and installing them.

Anyone that can give little feedback or have used or followed their instructions let me know

Comp engineering instructions:

https://static.summitracing.com/global/images/instructions/cee-3115.pdf