I posted a vid on youtube about how to format an unofficial CF Card (non akai and above 2gig).
http://www.youtube.com/watch?v=1qFV6lyIH0cAbout a year and a half later and I can 100% positivity state that my MPC500 will read every sample even if you go over 2gig (i only went up to 4gig), I have had over 3gig of samples on my current CF for over a year now and for a fact my mpc500 reads all of my samples.
(I wish I could claim the same success with the ram upgrade but unfortunately for my mpc500 both unofficial and akai official ram eventually caused my mpc500 to become unstable, some people can live with the errors that sooner or later seem to happen but I found them overly annoying so now i just make do with stock ram.)