What I meant to say was stitch in the repair piece, then use filler to smooth it out if it warps. With a hole as small as the one you speak of, you may just be able to MIG circles until it fills in. Weld a little bit, then let it cool, then weld a little bit, then let it cool. If you do quick, short welds, you should be able to keep the metal cool enough that it doesn't warp.