How Tall to Veg Before Flowering (Grow Cab/250W HID)

So I have a very finite amount of space, height-wise that I'm working with.

My grow cab's grow space is 5ft. Subtract the space needed for the hood and light (250w HID) and subtract usable space by a good 10 inches. So we're talking about 4ft from the bottom of the cab to the bottom of the light.

How tall should I let my plants get during veg before flowering to make sure I don't let these guys get out of control?

the rule of thumb is, when u flip your light to 12/12 they will tripple in size. besure to choose the right stain and you will be fine.

- but be carefull. Sativa girls can grow beyond that. Mine stretch to 5 times at least so i almost don't veg at all.