Grandaddy Purple (clones): please advise on size! who's grown these out? bay area CA

allright i've been vegging 11 GDP clones in 3-gallon pots under a 600w hps for two weeks now and they're at about 9". i was planning on flowering at 12", but the grow space is about 3x3.5', so each plant has about a square foot and i've been advised that this may not be enough. already topped em once too... am i in trouble? should i downsize to 9 plants and flip at 10"? flip 6 now?
if anybody's grown out grandaddy clones like this please share your knowledge in terms of stretch during flowering and space requirements.
and since all the factors are included can anyone estimate a yield from this space?

flip 'em all now. and bend them around to compleatlt fill the area with a nice even canopy

thats how they look right now minus two from the front. think i'll keep these 9, leave the lights off sunday, and start 12/12.
but seriously folks, if anybody thinks these are gonna be two feet across six weeks from now, YELL AT ME

How do they look now?