I am doing some sheetmetal work on my model a (chopping top, filling gas tank on cowl, etc). My question is what is the best size tungsten and filler to use? I am tacking and jumping around to avoid excessive warping. Using 2% thoriated. I have 1/16" and .040 tungsten. and all sizes of filler .020, .040, 1/16. What is the best combination? I have amps set at 50-60 range. Thank you for the help in advance.