Quote Originally Posted by ectoplasm
thanks for all the responses.

I can see that welding is really the way to go. So, is it necessary to take the panels and weld a backing?
if the holes are bigger than 3/16 make backers . you want to hop around keep the heat down.the back will rust lik dave S said so you want to seam sealer or use epoxies for sealing the back. any way you go .so you need to put some thing on the back or spray undercoating on the back side and call it good the best way is the epoxies like the west system put it on with a acid brush and you may want to add a thickener to it. keep it from runing. this will make it air / water tight or just cheap fiber glass resin works ok to i have did seams this way and hold up very good