Ahhhh, you are working each weld as you go. The shrinkage is easier to control and the gap may not matter, you are overcoming the shrinkage with your planishing. I am talking letting it cool, again, with a bodyman style I have been working on late models for years and in those cases there is VERY often no access to the back side on these butt welds, so the closer the gap the better.
I have to tell you, I too did a lot of work with the torch before I got my MIG. My first chop top of course was all torch. And I plan on going back to it when I finish up my truck (same truck, different cab) to my torch just for old times sake. I have a "jewelers torch" attachment that is pretty neat, I call it a "Poormans TIG".
I have only used it a few times and using .023 MIG wire as filler rod you could lay a tiny little bead with a pretty small HAZ.