Oh be sure to move around. What I mean is don't start at one end and go to the other all at one time. Jump from side to side and front to back spread the heat out. You will build up a lot of heat and can bow your frame. I've worked structural steel for 20 years I've seen welds warp some huge steel beams. Your chassis is critical to get right take your time and if you can weld it over a couple of days would be even better
