Weird problem: SCSI flash drive works but won't boot

[Stephen <stephenhd55@gmail.com>]

Hi everyone --

After many years I'm trying to get my beloved ROM 01 IIGS up and
running again.   I have a old SCSI drive but I fear it will not last
much longer, so I am trying to set up a flash hard disk using hardware
I already have.  I have an Apple High-Speed SCSI card connected to an
Accent SCSI PCMCIA card reader.  In the reader I have a 256MB
SimpleTech compact flash card via a PCMCIA-CF adapter.  The device is
self-terminating and I have it set for ID 6 (though I have tried other
IDs as well).  My High-Speed SCSI card is set to ID 7 (all default
settings).

In short, I can read and write to this drive in GS/OS just fine, but
weirdly I can't get the system to actually boot from it.  Here are the
details of this puzzle:

To set this all up, I booted GS/OS 6.01 (from floppy) and ran Advanced
Disk Utility.  It recognized the flash drive immediately and at the
correct size of 256MB.  I created two 32MB ProDOS partitions and
formatted them.  No problem.  Both drives show up in GS/OS and I can
read and write to them.  I then proceeded to do an "Easy Update"
install of GS/OS on the first ProDOS partition.  Install went
smoothly, no problems.  Sweet!

But upon reboot, the system hangs for a while (at the ROM splash
screen) and then moves on to trying to boot slot 6.  I can see the
access light on the card reader flash a few times, so it's trying but
nothing happens.  If I boot to GS/OS on a floppy, I can access the
flash volumes just fine.  I just can't boot up from them.

Also interestingly it appears that ProDOS 8 can't see these drives.
When ProDOS 8 starts up from a floppy there is a long hang at the
ProDOS splash screen and the drive light blinks; startup from the
floppy then continues.  PD8 applications like ProTERM and Apple's HS
SCSI utilities seem to see that there is something in S7D1 but can't
access it.  ProDOS 16 applications like GS/OS and ProSel16 can see it
just fine.

Based on what I've read about the CFFA card, I am wondering if perhaps
CF cards in general need some sort of special partitioning and
formatting that can't be done via the Advanced Disk Utility?  I
actually tried running the CFFA utility but it is CFFA-specific.
Apple's HS SCSI utility doesn't even see the drive.  ADU is the only
thing I could get to recognize the drive.

Any ideas?  Thanks for any advice!  It feels like I am very close
here.

--Stephen