One thing I have not addressed yet and is probably not relevant until the Ping returns are able to control the hacked continuous rotation servos, is that the servos themselves are not centered and I do not know how to do that.
What does "centered" mean for a continuous rotation servo?
If you are referring to the regular servo, you control the full range of motion. You simply write() for it to go to the middle of the range. Whatever the range is.