Okay, Mac128, here's my detailed test report using your Magic System 2.1 / Finder 4.1 disk and a patched HD20 INIT. Note that I put System 3.0 and Finder 5.1 on my HD20 to make the HD20 boot with your Magic floppy.
(1) Deleted "Dispatch Kernel" but left TFS & .Sony in the HD20 INIT via ResEdit. No "Disassembler installed" message inside the Welcome to Macintosh box, but I see the LED flash and disk motor access on my external 800k drive during boot. I can format 800k disks MFS! Yeah! But the HD20 won't boot with this disk. Instead the disk boots to the Finder, at which time the computer locks up hard, and the arrow cursor cannot be moved.
(2) Deleted "TFS" but left Dispatch Kernel & .Sony in the HD20 INIT via ResEdit. No "Disassembler installed" message inside the Welcome to Macintosh box, but I see the LED flash and disk motor access on my external 800k drive during boot. I can format 800k disks MFS! But the HD20 won't boot with this disk. Instead the disk boots to the Finder, at which time the computer asks me if I want to initialize the HD20 or Eject it. No crashes/lockups in this case, but of course, the HD20 won't boot nor is recognized at the Finder (most likely because its HFS formatted).
(3) Deleted "Dispatch Kernel" & "TFS" but left .Sony in the HD20 INIT via ResEdit. No "Disassembler installed" message inside the Welcome to Macintosh box, but I see the LED flash and disk motor access on my external 800k drive during boot. I can format 800k disks MFS! But the HD20 won't boot with this disk. Instead the disk boots to the Finder, at which time the computer locks up hard, and the arrow cursor cannot be moved.
And there you have it. So while it didn't give us a means of formatting the HD20 as MFS, it was an interesting set of tests. And originally, my HD20 wouldn't boot at all (the Welcome to Macintosh box would flicker and the computer would lock at that point). But before, I had System 4.1 and Finder 6.0 on the HD20. When I downgraded the HD20 to System 3.0 and Finder 4.1, I could make it boot using your Magic disk, so long as I had the unaltered HD20 INIT installed on the floppy.
(1) Deleted "Dispatch Kernel" but left TFS & .Sony in the HD20 INIT via ResEdit. No "Disassembler installed" message inside the Welcome to Macintosh box, but I see the LED flash and disk motor access on my external 800k drive during boot. I can format 800k disks MFS! Yeah! But the HD20 won't boot with this disk. Instead the disk boots to the Finder, at which time the computer locks up hard, and the arrow cursor cannot be moved.
(2) Deleted "TFS" but left Dispatch Kernel & .Sony in the HD20 INIT via ResEdit. No "Disassembler installed" message inside the Welcome to Macintosh box, but I see the LED flash and disk motor access on my external 800k drive during boot. I can format 800k disks MFS! But the HD20 won't boot with this disk. Instead the disk boots to the Finder, at which time the computer asks me if I want to initialize the HD20 or Eject it. No crashes/lockups in this case, but of course, the HD20 won't boot nor is recognized at the Finder (most likely because its HFS formatted).
(3) Deleted "Dispatch Kernel" & "TFS" but left .Sony in the HD20 INIT via ResEdit. No "Disassembler installed" message inside the Welcome to Macintosh box, but I see the LED flash and disk motor access on my external 800k drive during boot. I can format 800k disks MFS! But the HD20 won't boot with this disk. Instead the disk boots to the Finder, at which time the computer locks up hard, and the arrow cursor cannot be moved.
And there you have it. So while it didn't give us a means of formatting the HD20 as MFS, it was an interesting set of tests. And originally, my HD20 wouldn't boot at all (the Welcome to Macintosh box would flicker and the computer would lock at that point). But before, I had System 4.1 and Finder 6.0 on the HD20. When I downgraded the HD20 to System 3.0 and Finder 4.1, I could make it boot using your Magic disk, so long as I had the unaltered HD20 INIT installed on the floppy.