For a tough, light weight inverter power supply with more than enough power for you application, try PowCon. Esab also has a 350mpi power source that thier catalog lists at 101 lb net weight. I don't have any experience with that one though. I am also assuming that you have power available at the jobsite and are looking for a single or three phase power source, not an engine driven welder. If you are looking for an engine driven welder under 200lb, you can forget about it unless there is something a LOT smaller out there than I know about.

G Roberts

When I take my crew up high we have two choices, one is I have my Lincoln Ranger 9 gas drives on wheels and we set them up there with a forklift or a crane. The second is to use a generator and a long cord for our Miller XMT 304 invertors. This is not always practical, voltage drop is a concern when you run 500' of extension cord.

Have you looked at the Maxstar 200 ST? It is a 200 amp stick machine that weights 32 pounds and will run on 120 volt to 460 volt single or three phase. This sounds like what would fit you needs. I have welded with this machine and it does an excellent job.

My approach is different.
You may use welding machine on ground level.
1) use high capacity welding power source(min. 350 amp) to get enough voltage.
2) use 120 sq(mm2) earth cable from your power source to the roof.
(I expect 50 feet)
3) use 80 - 100 sq torch cable from your power source to the holder cable. use standard torch for easy handling for welder.
80-100 sq is three times bigger than the normal cable, which allows you three times longer extension without voltage drop.
You may use much large dia. torch cable from power source to the roof edge.
4) divide four or more section to set the welding power sources.

dong won oh
Seoul, Korea