I'll be growing some white widow by hydroponics and at most i only want it to be around 2.5ft tall after vegetative and flowering. how much taller should i make the box to accommodate that? the lighting system with reflectors and all will be 6", so should i just make the box six inches taller so there is room between the top of the plant and light. and by passive intake do you mean i should just have some sort of opening in the box to let air flow in naturally?