Thats some pretty impressive growth you have there tap!! Well done.
I was wondering a similar question myself, being in my first grow season my 12 plants (on day 23 from seed) are between 6 and 10 inches tall now and very bushy & compact, my grow room is five foot tall and I wasn't sure at what stage to flower them at, im using 400w hps & C02.

MNSN