Connected the drive (data and power cables) to DF1: port of A1200 with Kickstart 3.1 and Workbench 3.1, however, I could not make it work as HD drive.
how you connect it to df1: , can you make a picture of it , i think you mis something , the drive are test befour i ship it , normale if you use the drive as df1: you need a pcb like the other amiga drive that connect on the extren disk drive port , when you use ( like the 2000/3000/4000 ) a intren cable for df0 and df1 , then you need twist the last connector on the cable for df1
I systematically re-checked the cables, connectors, jumpers, and combinations of the settings, and finally got the drive working as HD when:
- connected to DF0: port
- jumper in position 1 (setting for DF0

Under these conditions it works as HD even when another standard DD drive is connected to DF1:
When connected to DF1: through a cable with reduction from external to internal drive connector (yes, it includes a PCB and looks similar to what
@livewindarefail posted), the drive doesn't work as HD. Its behavior is:
- not working at all if jumper is set to position 2 (setting for DF1

- working as DD only if jumper is set to position 1 (setting for DF0
So, the good message is that the drive works as HD when connected to DF0:. Initially I had problems even when using it as DF0:, but either I must have mixed up some settings during my initial tests or something has changed when I opened the drive, and played a bit with the wires and connectors and then reassembled everything again.
The bad message is that the HD drive mod is not compatible with (at least some of) DF1: external-to-internal floppy drive reductions used on A1200. But I can live with that.
Thanks for your support and patience.