David, good post just thought i may be able to add to it as I have a few of the RZ manuals (prism, lenses, body, back etc) that may be of use to people. i have got them on PDF to make it easy to send.
You can get a lot of those manuals free in PDF format at the Mamiya website. I got mine for the Pro S there. Probably there are some for the RB Pro and the RZ too. Ric.