how much can i expect them to grow??

I have a 50/50 strain which are pretty bushy and squat at moment been runnin a 600w hps 24/7 now I want to go 12/12 how much can I expect them to grow during flowering period, they are about a foot tall at moment, its just my cabinet is only 5' so am limited to space I am growing in dirt and am feeding as amd when. Thanks and peace. Yorkie.

If you keep the lights as close as possible until they start to flower, that will help keep the stretch down. Just make sure the leaves are not turning yellow (light bleaching).
As for what to expect, that a hard one being every strain has it's own way of doing things.

Thanks, yer I have been keepin the lights low and there is no problem with heat so will giv it a go, thanks again! Yorkie.

Every grower effects the outcome also, lets not forget that.