Update:
I've cleaned the internals up considerably, did some shimming, re-greased and reassembled. After that I chrono'd it at 365 - 367 fps.
The noise level seems to have dropped a tiny bit due to less rubbing on the cutoff lever. I also tried to get more clearance between the gears than I saw before.
I didn't measure RoF before doing this work but it feels like it's dropped a bit, probably due to my shimming. I will probably give it another try some time this week to see if I can get the best balance between RoF and play / contact.
Some notes from re-assembly:
1) This thing is really tough to get back together compared to a V2. The trigger is really really tricky to keep in place while sealing the box and holding everything else together. I feel like I've completed a rite of passage just by getting that trigger spring and those two trigger shafts to align while holding the main spring, cylinder and just about everything else with my greasy hands. I read warnings on various forums, and they were all correct. Prepare for some hair-pulling...
2) If you take this thing apart make sure to take lots of pictures of how the wiring is set up or it will be hard to put back together. If the gearbox is jammed into the lower receiver without care, the wires will probably strip.
3) It appears to be extremely easy to bend or damage the selector plate during re-assembly. I had to go very slowly and watch both sides of the gearbox slide in to ensure everything "slotted in" correctly.
4) Aside from the gearbox shell itself, the motor cage seems like it might be the first thing to go if anything metal were to "go" on this gun. The bottom of the two halves of the cage has one side that bends out ever so slightly and has the seam open into a 1mm gap when the gearbox is out of the grip (I suspect the two halves are pressed together while in the grip. Hard to say).