"APC Bass notes just seem to play some or all of the notes within the diminished(7th) chord, as I would expect. The order in which they are played depends on the inversion of the chord. If I was composing a Bass track, I would normally do the same, since any other notes seem to be discordant."

Yes, Bill. That is what I have found. And, that is why I have problems accepting the use of the root note of the chord in the bass line where a 7-9 occurs. It sounds discordant to me. I tend to want to walk the bass line toward the next chord which would usually involve a D. ie: C in the measure before the C7-9, C# in the measure with the C7-9 and a D in the next measure.