im gona just try it see what happends im flipping mine very soon just hopeing thay dont just stop at the hight that thay are at i have never use this b4
They are not going to stop growing just because you flip them back. Look for at a minimum a doubling of their height from the time you flip to about week 5 of flower. Some strains, especially those that are heavy sativa, will actually put on 2/3rds more height.
MJ grows as long as its receiving light, doesn't matter if it's 24 or 12.
If you're worried about reaching beyond your height limitation give them a topping before you go on 12/12, preferably at least a week before, which will also add colas to the plant. Oh, and do a massive reduction in your N. During flower try to keep your N at 4 or below.