Out of the IC instruction book for a 660-009
660
2 lamps 16' max 2 X 8',6,5,4 or 2
3 lamps 15' max 3 X 5',4 or 3
4 lamps 16' max 4 X 4',3,2
Go to the IC web page for wiring three bulb. I don't think the 660 drives the longer bulbs as well as the 4' but I thnk they say you'll get 90w-95w out of them.
HTH
Tim