Keeping plant size under control

[Sochi]

I have five Green Crack Seedlings--all from CKS and all germinated perfectly. The photo I attached here is one of my seedlings. I think it suffered some nutrient deficiency at first because once I gave it a light feeding, it seemed to have recovered.
I would like to delay initiating the flowering stage until mid-July (travel reasons are dictating this decision). By July, my plants will be 4 1/2 months old. My room has 8ft ceilings and I have a LEC 315W lamp that takes up some vertical space. Room dimensions are approx 9ft x 20ft.
I have read that plants will sometimes double in size once 12/12 is initiated, so I want to be careful about the height of my plants and would like them to be at least 18 inches away from the lamp by the time I am ready to harvest.
What advice/thoughts do you all have about keeping the height under control? Topping? I don't know how tall these plants can get but I'm hoping some of you have experience with these and can give me a sense of what to expect. Thanks

 

[Weaselcracker]

Here are some methods I use. Dimming the ballast to reduce the lighting wattage, supercropping, LST (low stress training- meaning tying them down), topping, reducing feed a bit, keeping them in smaller pots as long as possible, reducing the total number of light hours, lowering temps a bit, and (most effective of all) scrogging.

 

[Sochi]

Here are some methods I use. Dimming the ballast to reduce the lighting wattage, supercropping, LST (low stress training- meaning tying them down), topping, reducing feed a bit, keeping them in smaller pots as long as possible, reducing the total number of light hours, lowering temps a bit, and (most effective of all) scrogging.

Thank you, Weaselcracker! I just started looking through your journals. They are fantastic

 

[Weaselcracker]

Thanks Sochi. Another last ditch thing is do sometimes is to make a clone of the plant then throw away or flower the big one. That's last resort stuff though, and probably doesn't apply to your situation anyway.

 

[Sochi]

Thanks for the option of last resort. You never know when that might come in handy! I'm definitely studying up on supercropping, LST, and scrogging.