I'm making some progress on the X1215 Imager. I can send commands to the drive to select heads, step to tracks, and to start reading.
Connecting the oscilloscope to the output of the read amplifier, I can see the data go by. The encoding is very primitive, which makes things easy. One bit-cell takes 400 nanoseconds. If there is a single flux-transition in a cell, it reads as a 0, if there are 2, it reads as a 1. So, on the picture above you can read "10100" from left to right.