Any good welder with common sense will keep from burning things down. Anyone bragging that they welded the coach without taking provisions to prevent stray current spikes are kidding themselves. Just because you have a return clamp close to the work means nothing. Preventing ground loops are a science with a little luck and there's never any guarantee the return current and welding spikes are heading from the frame and straight to the clamp and not taking an alternate path down low loss copper and through unspecified electronics to stir things up.