hey mN, VERY NICE GROW! it is an exact blue print of my intentions. I see you refer to your cab size as 14x28...what is the third dimension. how many cubic feet in your cabs and how much air do you move. my question mark key doesnt work, so ignore my lack of proper grammer. also,m what height from your plants is your hps...im trying to design a cab with the absolute minimum heightr and maximum lateral space for a 400w hps bulb. your screen is 4 feet square (well, parbolically shaped of course) do you think a larger screen would equal more yeild or is the use ful light sphere maxed out in your design. congrats again, you are by far one of the most useful ppl on this site!!!
~I think the height is 72" for the whole cabinet height. Not sure how big just the grow chamber is, will have to take a measurement when lights on.
~I have a 300cfm inline fan pushing air through a big can carbon filter in the top of the cabinet. There are holes in the top of the cab with register covers to allow that air exhausted into the chamber to exit passively (less noise).
~I am about 20" or so from the lamp center to screen. As the plants grow they get closer to the light. However, if you air-cool the light separately from the grow you could get much closer. Cruizer has a great journal with his cab and air-cooled lights.
~I could handle probably triple the square ft of screen if I had the space. I think that footprint would max out the usable light in this setup. Meaning... that if I had the space I think I could get very close to pulling a pound from this 400w lamp.
Thanks for stopping in, glad I can/have helped you out. Half the fun is engineering the setup.