150w HPS

so i have a grow box that is 4ft tall 2ft long and 2ft. currently im growing two plants under cfls but very curious in a hps system. what i am wondering is how close could these lights get in well vented sealed box? id like to grow my plants to be about 3 1/2 ft but i dont think i could achieve this with hps in the box i have. what do u guys think?

The hood for the light is gonna take 8 inches at the least LST you should bd ok unless u growing a sativa monster

Check out my sig bro. I'm using a couple of 150w HPSs. You can keep them about 4 inches away if you can keep the room temps down

I have mine at about 5-10 inches away and I'm not seeing much improvement . Are they too far away ?