On 2", I only put 2 tacks. Top and bottom. Put your purge line in on one end and tape it up real good where it won't fall out. I like to use the big gas lens on the end of my purge line. On the other end, cover completely with maskin tape. Then using my tig wire, punch a few holes in the tape. This will allow excess gas to escape. Then tape up your tacked test piece, running the tape from top tack to bottom tack, both sides. Then start the purge. Peel back enough of tape to start from the bottom and go up to 3 o'clock. Just lay your tig wire just inside the bevel and just run over the wire but make sure you are tying in on each side of the bevels. Then do the same thing on the other side, going up to 9 o'clock. By now, your gap will close up, maybe a loose 3/32. You can use 1/8 wire, just lay it in the bevel and run over the wire or go to a 3/32 wire and feed it. Either way, it should fall right in there. Just remove enough of the tape to weld from one point to the next. Once you get the root in, leave purge on and hot pass. Once you get the hot pass in, you can remove the purge and the rest of the tape on the ends. The reason for the purge, the root on your stainless will what we call "sugar on ya". This will end your test pruddy quick.