A-Body Frame Rail Connector

i still have negitive thoughts about welding these in on a rotiserie , ive heard when on them the body might tend to sag or twik a little , i was told to lower down to the ground and install the springsand stands in back and jack stands in front under frame and let sit a week or so to let it respring itself for a while, then tach weld the connectors and then raise and finish weld , can anybody add some view point to this , the latter does sound logical ? thanks dartman 440