Just my thoughts, but that length X depth and short height I'd see probs from the get-go.
w/39" H you'll be having 10 for the light, 10 for the pot, leaving 19" for plant maybe?
The 15" depth is do-able, but I'd consider it tight (for my taste).
4 ft long? both sides would be starving for light because of short heigth In my thoughts.
I'd go with a ratio something like 2 times the width for figuring heigth. Depth can be up to the same as width.
If I were to consider a box like that I'd probably be thinking 3 - 100 watt HPS spaced evenly across the top to better satuate (flood) the grow more evenly. But, I'd be concerned about penetration on them little 100's (don't know enough about them really).
I'm trying to finalize my plans for a flower cab. Presently my dims are around 28 X 28 X 50 high. Thinking a 250 HPS will do, but still working the plan out before starting.
