I could, I'll have to order some lights and sockets first mind you. I checked Fulham's website and indeed they'll point you to a WH5 if you want to run 4x24w, and a WH8 if you want to run 6x24w. Both the 7 and 8 are 220W but I guess the 8 has an extra set of red leads. The 7 can do 4x39 or 4x54 though. So it seems I have just a little bit too much ballast for what I want to do, or "not quite enough" ballast (ie., I want to run 8 24w anyhow so running the 6 lamp config would be OK but seems I'd still have to buy a second ballast anyhow so maybe the trick is sell the 7 and pick up two 5's.)
