Frame connectors on a rotisserie car?

I think I know the answer? I have my car "69 fastback" on the rotisserie and I would love to weild in frame connectors in now while its on there.has anyone done this with good results?Or does it have to be on its wheels?I hate like hell to throw the car back together to install the sfc's.only to take it all back apart to finish restoring the car.Any advise????