Casio CZ/ VZ/ FZ - Pro Series

>Are there any others with tips on getting FM bass out of their CZ?

I think one important thing to note is that FM synths can't easily produce 
broad-spectrum sounds (looking at graphs of the Bessel function stuff 
there's not really anything that resembles something like a saw wave or 
square wave spectrum).  Getting the same harmonics shouldn't be too hard- 
modulator-carrier ratios of 1:1 and 2:1 correspond to saw and square waves, 
respectively, and more complex or inharmonic ratios can be gotten with ring 
mod.  It's the amounts of the harmonics that makes it difficult.  Softer 
sounds without a lot of high harmonics should be fairly similar, it's the 
brighter sounds that I think would be more problematic.  Anyway I don't have 
a CZ so I can't be a huge amount of help.