how tall can i let them get?

what is the max height i can start to flower my plants at? im using 4 inch sure to grow cubes. im just scared of the plants outgrowing the cubes so to speak, but i just want them to be as big as possible cause i can only grow once in the next 6 months.

using ebb and flow, with 400 w mh, going to switch to hps when flowering.

thanks everyone

Don't worry about them outgrowing the cubes, worry about them outgrowing your ceiling and your lights.

thanks for your response....my cieling space is practically unlimited when it comes to marijuanna growth.... so about my light then, around what height does a 400 hps become impractical for use then?