Resurrecting an old thread, in case anyone else with an A4000 is googling and stumbles across this thread.
I went down a very very long rabbit hole. I have an A4000 with 3.1 ROMs installed and a 16GB CF card connected to the IDE Master on the internal IDE port. I tried several combinations of scsi.device and filesystems and this is what works really well for me.
1. In WinUAE, I installed ClassicWB Full (you could probably use ADV but I didn't test) hardfile. I bought Amiga Forever so I had the Workbench 3.1 files legitimately ;-)
2. I booted up the ClassicWB install and then copied the scsi.device that is included in ClassicWB in DH0:MyFiles/LargeHD/128GB_Support/SCSI_v44_45_ChrisToni to devs:scsi.device. When you reboot ClassicWB you should see scsi.device 43.45 when you do a "version scsi.device"
3. reset the WinUAE emulator and then configured it to use my CF card as a hardfile. The instructions here are useful:
https://16bitdust.wordpress.com/201...6-gb-compact-flash-card-with-winuae-and-pfs3/. It's key to start WinUA as administrator.
4. Using the above as a guide, I used the HDToolBox in the DH0:Tools dir to set up pfs AIO on two partitions, the first was a 2GB partition and the second was the rest of the CF card. Note that when you're resizing things it wraps at the 4GB mark, so make sure you size the first partition down to the smallest then increase it slowly until it gets to about 2-3GB (2GB seems enough for wb and apps).
5. I use PFS3 not PDS3 as the device type. PDS seemed to have trouble before I updated the scsi.device, though I suspect it might work now, I haven't tried. Honestly the performance doesn't suck.
6. It's good to note (as noted elsewhere) that it's easy to forget to hit enter on a text field. If you don't the value wont be saved.
7. Once the CF disk is partitioned, you reboot, and you should see DH0 and DH1 appear as NDOS.
8. I didn't trust the ClassicWB format, so I used the CLI: "format device dh0: name "Workbench" quick"
9. It should be noted that as your booted workbench may be DH0 then the new device might be DH0_0:, adjust accordingly.
10. Copy the complete workbench over; "copy DH0: DH0_0: all clone".
11. Turn off the WinUAE machine and remove the hardfile, leaving the CF disk device, and then boot it. It should boot up perfectly fine.
You can then plug the CF card into your machine.
I use one of these from amazon. It worked perfectly, and mounts easily into a spare slot in the back of the machine.
I just copied about 4.5GB of data to my DH1: and nothing broke, so it seems to be working well. I get 1.5MB/sec using SysInfo from a SanDisk Extreme PRO 16GB card I had lying around.