With added '245 chips between my memory board and the synth's data bus...
...it works. Full 8MB recognized as of two nights ago. I haven't yet tested loading up 8MB of samples, or validating the passthru to the waveform card works either.
Hope to get the PCB design revved with the ECOs and sent off before Knobcon this weekend, so I can have boards late next week from China. That'd be lovely.
If only my physical health didn't keep getting in the way...