Hi all, haven't posted for a while but I still lurk. There is a great discussion going on over here at Vintagesynth forum about RZ mods, including sample RAM expansions and sample dumping and loading via MIDI sample dump:
http://forum.vintagesynth.com/viewtopic.php?f=1&t=104766
Check it out! Also remember I have the RZ-1 service manual and schematics here on my band's website:
http://www.warningwillrobinson.com.au/manuals
Cheers, Graham