Mike,
That 1/8 stuff is actually 11 gauge, the ERW 1010 common tubing is by gauge and that is as thin as it goes for that size. You can get .083 wall, which is a typical size used in chassis construction, in a more expensive alloy and DOM, but no need to bother. There is less than half a pound difference per foot in the two. Even if you use 20 feet, you are still looking at less than 10 pounds difference. The more important factor is whether you are going to mig or tig it. If it is probably mig, you will be glad to have that extra wall thickness.