I've decided to go ahead and start this rack build thread now that I have almost all of the parts in. I am not going to build all of the shelves in on this first build, so that I can keep the humidifier on the bottom shelf of the rack for now due to space constraints, however it will be 8 shelves high in total, and 72" tall without casters. I have a thread up in husbandry about the humidity control system in and of itself, so that won't be listed here except how it's all installed on the rack.

For this build I am using Hefty brand locking handle tubs. I specifically went with these tubs as they are fairly sturdy, well priced and they are designed so that the 15qt, 34qt and 52qt tubs are the same height, share a 16.5" dimensions(width for the 34 and 52, and depth for the 15qt) and are designed to stack, so each shelf can hold one 52qt, one 34qt and one 15qt or three 15qt tubs and be completely interchangeable.

Parts List: My build(full rack)
6(9) 2x2x96"
4 2x3x96"
2 sheets(4 sheets) 4'x8' 1/8" Hardyboard
WH13001 WillHi 12v hygrometer controllers
ITC-1000 Thermostats
Heat tape, I'm using THG, but design will work with flexwatt almost identically.
Humidifier(see my other thread for DIY cool mist humidifier that puts out HUGE volumes)
Optional - 1 sheet backerboard or pegboard to enclose rear
Optional - 40lb/ea or better casters of your choice

Cutting of the lumber and assembly starts tomorrow, will update late afternoon/early evening.