Light height for flowering

I have another question. I only have about 4" more I can go up before I hit the ceiling with my 600 HPS light. I have 24" between the light and plant. The only problem is that I am only 12 days into flowering. How much taller can I expect it to grow? The planter is sitting on a table just above the 18 gals. reservoir. I might be able to take 3" off the legs to put it right on top of the reservoir. But that is about all the extra length I can find. Can I tie the top down or is that something you can only do in the veg. room? Thank for the suggestions in advance.

Floering plants will double to triple in size from when you put them into flower mode. LST can be done, but causes some stress on the flowering plants...

LST still sounds like my best chance of pulling this off. Should I cut the top down futher? I've only cut the top once and it was only to get two buds at the top instead of one. What would be the risk if I did cut the top down some more?

Do not top when in flowering...

OK. Topping is bad I take it?

It is too stressfull for the plant.. LST is a little stressful, but not nearly as stressful as topping... Plus, you will be chopping off the main bud site...

thanks for the help