A small welder has the power for sheet metal, and if your just hanging sheet metal and the weld cracks, you may get a crack in the paint. If your welding a rollbar or suspension that's another story.
https://www.youtube.com/watch?v=cMoXOky6buA I've seen bad welds made with top notch equipment.
If you use the machine properly and within it's designed limits you should be fine.
Use ANY machine improperly and you will have problems.
Use ANY machine outside it's designated limits and you will have problems.
