Hello Cactusthewelder, I don't believe the Hobart Fabshield 21B is qualified for FEMA, that's why he is using the ESAB Corshield 8.
Firstpass, I do believe that 1/16" wire will work reasonably well for those welds. Also pay close attention to your stick-out with this wire, I believe it is called out at between 3/4" and 1". On any verticals that you run, I would suggest a slight drag angle instead of a push and you will likely want to get a hold of some scrap and work with the suggested settings a bit, the Coreshield 8 can be a little bit finicky and have a fairly narrow range of voltage and wirespeed to come out the best. In the past there have been a few individuals on the forum that have quite a bit of experience with this wire, hopefully they will chime in here and give you some suggestions as well. Best regards, aevald
Fabshield 21B is not a T-8 wire. Fabshield 71K6, Fabshield 3Ni1, and Fabshield 81N1 are all wires that you might consider. They are commonly made as 5/64. They all have a fairly narrow range of acceptable voltage/amperage settings, but once you get the hang of running them, they aren't a problem.