With all due respect Jon, without a fair amount of practice, a first time oxy-acetylene welder, has about the same chance of success as me landing a 747.
I have to disagree with you. If for nothing else everyone should have a small oxy-acet kit to use with a rosebud to heat things up. I have brazed cast iron using brass with oxy-acet and have gotten better results than trying to weld it.
Add a cutting torch to the kit and it provides a lot of time saving in cutting metal and/or cutting old brackets off, stuff like that. Seems you have some time on oxy-acet, so not sure why you're so dismissive about it.
I bought a small set off craigslist, took it to the local welding shop and had them go over and make sure everything was in good working order, and I get my gas from them. Been about 15 years now...
My recommendation is to braze it. So much easier to learn and it takes much less heat. Note that you still need to cool the panel during this process or it will still warp. I use a rung out towel dipped in water.
Personally I wouldn't braze that, that's not how people do body work. May work, but still not the way it's typically done. What I have seen is to pull it tight, and just put a few tacks, spread out to hold the seam, and continue to fill the seam between with more tacks, letting it cool, and continuing to tack until the seam is filled in, being very patient to let it cool. Say you put a tack at each end and one in the center to start, then fill in the space with tacks. After the seam is filled, grind the tacks down smooth. At that point you can't see the seam. You could weld it with oxy-acet as Jon suggests and that will work better than brazing, IMO, but this is not something I would braze, I would only braze cast iron. Also, if you braze this you will have the color of brass mixed with the the color sheet metal. Could look like a Damascus tattoo on the sheet.
You could use a small 1/16" 6011 and stick weld it, dropping the amps down to about 50-55 so you don't blow out the sheet and use this tack method I describe, but these days it is more commonly done with mig. I would do it with tig, I weld with stick and tig, and as I like to say, I don't need mig 'cause I get my snap/crackle/pop from stick.
Remember that stick was used to repair body work like that for years prior to mig and tig hitting the scene. AFAIK, that's how the majority of body work was done using the tack method and grinding flush. Maybe someone will correct me if I'm wrong.
