The 430 will operate up to four 24" VHO lamps in the schematic above. But, for T5 HO lamps, the maximum number it can power is two. To run four T5 HO lamps, you would need to replace your 430 with a 660 or buy a second 430.
Both the 430 and 660 ballasts drive 39 watt T5 HO lamps to about 60...