A-Body Frame/Body Jig

This guy has a whole series on his 72 rebuild, including some details on building his jig. In this one he's doing front frame work.

He is holding the car by the rails in the front only, While he is repairing them? I don't know if that would be a good idea. The body should be setting on 8 strong posts with a dowel in each specific frame hole to hold the car square. Also a straight K-frame should be bolted in with the tapered original bolts while rails are being assembled to keep the rails square and in position.