Thanks but I can't connect the transistors to the anodes; I need to connect those to LED drivers. Basically I'm building a smaller (16x16) version of EMS's Peggy.
Now I think the problem is just transistor selection, not circuit type.
The spec sheet says maximum current of the PN2907a is 800mA, well above the 480mA (16 LEDs @ 30mA ea) I need. But after spending the evening googling around, now I think the important spec is power dissipation, and 480mA * 5v = 2.4W, well above the 625mW that the PN2907a can do.
So I think I just need to find a different PNP transistor, one that can handle that much power?
Thanks,
Chris