In all honesty I would not build a 6qt unless you plan on big time breeding and selling. Our little ones moved out of the 6 qt tubs quick! A 16 Qt something like this:

Will hold them up to around 800 grams and you just make sure to use small hides and a larger water dish to take up space until they reach about 250 to 300 grams.

Then from around that 800 gram to about 1500 grams we use 32 QT. After that they go in the big 41 Qt tubs.

I do have a 12 unit 6 qt rack that is sitting empty right now since all our balls have out grown them. Once we start breeding and have enough eggs in the incubator that selling off our hatchlings after 3 or more good meals is what we want to do I will have to build more 6 Qt racks. Until then they are pretty much a waist of space since most snakes will out grow them in 3-4 months if they are being fed for growth and not just maintenance fed.