Has anyone here considered cutting a hole in the bottom of the Rubbermaid tub and dropping the plant's pot down into it? You would have to support the rubbermaid tub with something just as tall as the flower pot, but it seems to me as though you would have much more room in the growing tub than if you had a big flower pot inside it.

Also...

Good or bad idea:
Place a tub of dry ice near the intake as a poor man's version of co2...