Hi man, how it going? I'm pretty familiar with growing in small spaces. I have a cab the is 11" x13" for 143 sq inches. I run 4 plants at a time in it, lol although the below pic is only 3, 1 went beast mode on me. What is the vertical height of the cab?
A few ideas for the light would to go with that
@Herbisaur said, and on the sides of the cab you could put a series of screws going up the wall. Most power strips have notches/screw holes in the back so they can be hung. By doing this you could move the light up as the plant grow.
You could take a piece of thin plywood (~12' x24") and attach the lights to it, and then use it as a false roof. You could use chains/rope/ratchet hangers to raise the lights.
If you are going to mount the lights horizontally I would make sure the roof is reflective. The sideways bulb will only be giving 50% of it's power in direct light. The rest needs to be reflected back down as much as you can. If it is already painted white I would not worry much.
Do you plant on running 2 pots in general? You could take 2 power strips and zip tie them together, back to back. Maybe put a piece of wood between them and use that to hang it. Use 2 socket splitters (Y) and get 6 lights total per light bar. (each side would use 1 splitter, and 1 socket plug for 3 lights)Then hang it horizontally above a pot. (make 2 total, 4 power strips, 8 socket/plug adapters, 4 splitters, 12 cfl) If you did something like this I would just use low wattage cfl. Using 23w cfl would give you 276w. It would get hot, but if well ventilated you should be okay. That does depend the cubic size of the cab though.
With the small space the best thing you can do is try and keep the canopy even. If you are able to do that you will be able to get the lights closer, and allow the plant take up more light. If the plants are untrained, you'll get the typical apex cola, and it will be taller than the rest of the plant. Have you read anything about using LST yet? A good place to read for idea would be in PC grows. Most times those plants are almost grown sideways to save on height.
If you have any questions feel free to ask. Till later, take care.