B3 uses 18 gauge (.065"w) on their frames. I used 16 gauge (.083"w) on my 3 tier. If you are going to have your frame on casters it can't hurt to go a little on the heavy side. Less chance of burning through with the welder too.
Heros are made 10 gallons at a time.
Kegged/On Tap - Double IPA
Conditioning - Orange Ale