Only problem I have with the welding is you should be wearing a full face-mask and you don't touch the rod like that. I can see arc-welding being done on some structural joints with a followup technobabble to seal and anneal the joint.
*shurg* Arc welding is an old old process by now, it's a very stable controllable process now, a skilled welder can weld anything to anything and make a nice smooth joint doing it.
While stick-weld is one of the most dramatic in terms of sparks second only to oxyfuel cutting I would have been running a TIG or MIG welder. Better joint better control.
*shrug* Overall it's a minor MINOR quibble. I enjoyed the trailer for what it is.