No. The HFS "single pixel" does not show up when I use Finder 4.1 in conjunction with your System 2.1 (or System 2.0). So when I said, in my posts above, that I checked my formatted 800k disks for that pixel, I was implying that I had booted with a more modern system disk that will show that HFS pixel.
As to the ResEdit hacks, I will try the variations you suggest when I find the time over the next few days (hopefully today, if I can) and report back here.
And yes, my HD20 does have a System and Finder much more modern than the S2.1F4.1 disk you gave me. I am using Finder 6.0 and I think System 4.1 (I'll need to boot my Mac to confirm the System version). But again, this is more modern than the boot disk I was using. Nevertheless, I have always used two different 400k HD20 INIT boot disks without problem to boot from my HD20. One of those floppies has Finder 6.0 and System 4.1, while the other floppy has Finder 5.5 and System 4.1. So this shows that the boot floppy will still hand over control to the HD20 even if the boot floppies Finder is a bit older than the Finder on the HD20. As to the System being older, I will have to test this further and see what happens.
Thanks.