I too have been having a helluva time trying to get a SCSI<>IDE adapter<>IDE<>CF adapter to work in my A2091. Same sort of problems as you, but I can get the drive to be recognised. Just when I go to format, I always get bad checksum errors. This and most of the time, the last partition will not be recognised - no matter how small it is.
And no, you should not need a GVP install disk for this, so long as you're changing HDtoolBox to gvpscsi.device.
Have you inserted the card into a PeeCee or Mac and formatted it as a FAT drive? Sometimes, with too much
monkeying around with it on the Amiga, I found that I needed to reformat the CF card to FAT before it would
be recognised by HDtoolBox.
Was this part of the thread where Mozzerfan gave you all sorts of great tips? Including the jumper settings on your card?
The SCSI<>IDE adapter I have NEEDS to be set to work as a SCSI unit, else it will not work at all. In other words, the way it is shipped is ATA or Ultra mode. That needs to be changed to either SCSI I or SCSI II. Both seem to perform as poorly in my system.
Good luck! Be nice if we can get this straightened out sometime this year! lol