For a higher ROF you want a faster motor (obviously) and maybe different ratio (high speed) gear sets, also a 9.6 voly battery is not a bad idea. Remember the whole big to small, small to big thing with gears? That'll greatly improve ROF but sacrifice torque (that's okay, you just can't have both amazing torque and ROF.) Also make sure your shimming is fantastic. If I was doing this I'd get a PDI 140% spring, a Systema Turbo motor and promethues high speed gears. I would also invest in a crane stock and rewire to the back so I could use a LARGE 9.6 volt battery. A tightbore won't gain a lot, but if you've got the money, hey why not. Leapers makes decent, cheap red dot sights, or you can go with guarder if you've got the money (damn good red dot sights.) Of course for the upgrades I'm talking about you'd need to be either a good AEG tech or VERY mechanically inclined.... Mechbox.com will help a lot with their disassembly guides.