Jump firmware versions

My brother has an NEC ND 3420A with the 1.04 firmware. He just flashed it with an RPC1 firmware. It removes the riplock but he is still only ripping at 4.0 to 7.4 and back. My BenQ 1640 rips at 7.4 to 12.6 and back.

So my questions is, what speed should he expect with that drive and would it help to flash it with the 3.04 RPC1? Can he flash it with the 3.04 RPC1 without hurting it?

Thanks for any help you can give.