G'day mate,
and welcome to the site. that buggy top will look wild when its finished. I have worked building custom commerial kitchen in the past and when we need to build long table tops we would butt weld the 1.2mm stainless using a balanced welding style. 2 things i would recomend for you when your oing your top is (you may already know this but I will say it anyway) 1. Clamp a peice of copper underneath your job to draw the heat away and distribute it evenly and 2. on long weld I would weld an inch then move along the weld another 8 inches or so then weld another inch and repeat the process untill you have sort of stiched the joint the entire length. then move back to the start and weld the next inch, then move along and weld the next inch next to your second stich. Just do that until the joint is fully welded. this will stop the heat in one area getting to much and distoring your weld to much. When your weld your joint if moving right to left I would start your stitch 1 inch to the right of your intitial weld and weld back towards it (weld right to left).
I hope this makes sence it did to me as i was writing it...
. if it doesn't let me know and I will try to explain it better.
Cheers Dale