I have not seen a CSL unit in person but Im willing to bet that you wont easily be able to put a MH
bulb in there with out doing some serious DIY
work on it.
How much space is between the PC
bulbs? One of the hurdles you will have to overcome is mounting the bulb socket in the fixture and then venting the heat. I guess this unit has afan and some vents?
The ballast for the MH
will have to be remotly located and holes will need to be drilled into the lighting unit to allow running of the wires into it for the socket.