Hi Marc,That is excellent to hear Jack !!! ... my camera was a AFD-II with a Leaf Aptus 75s, and I was using the correct module on the Metz 54 and the ISO defaulted to 100 on the flash. Any ISO was okay as long as it was 100. I went around-and-around with Metz and Mamiya tech support ... and finally gave up.
That's interesting... Could have been an issue with the Aptus back or the module. I have seen reference to two different modules for the AFD, one is the 3952 and I think the other was a 3951. Anyway, I have the 3952 module on my 54 MZ3 and all I do is set the flash to TTL, it reads the ISO off the Phase back directly and inputs it to the flash. If I am at 100, the flash shows 100, if I switch my back to 200, the flash reflects that change immediately and displays 200. The auto zoom feature works too, zooming to the mounted focal, aperture set on the camera is immediately reflected on the flash LCD and of course when the flash is turned on, the shutter speed sets automatically on the camera.
HOWEVER, there is one small nit I've found with the Metz: as you know, you can set the focal length display to match different formats. But if you set it for 645, for whatever reason the auto zoom feature stops working. Manual zoom works fine, but the head won't set the focal automatically as you change lenses. However, with the flash configured for the 35mm format, auto zoom works fine but displays the 35 format equivalent focal for the lens you have mounted. (For example, if I have my normal 80 mounted, the flash display shows 50mm, mount my 210, the head zooms to 135mm.)
Aside from that, it works like it's supposed to, and more importantly, I get excellent exposures AND excellent WB using the daylight setting on my back.
Cheers,