I beleive that the 2.1gigabyte harddrive size is a limitation of the device driver inside the rom onbaord the ADIDE. Not a limitation of the AmigaOS version ( altho older versions have their own unique limitations )
To setup the drive using the ICD format utility ( gets the mickey mouse award if you ask me! ) you need to run the software once, get the ID of your drive from within the device scan, then edit the parameters for the drive in the text file. This bipasses the BIOS drive number BS
On your drive itself will be the heads/cyl/secs
insert these into the text file under the correct description types ie.. scsi or ide sections
example:- inside icdfmt.dat
******************** IDE DRIVES **************
ST9190AG 16 00873 024
above is drive ID, heads/cyl/sectors per track, with the correct information typed into the text file, your drive should be recognised by the software and setup normally for partitions etc
Hope that helps
Az
P.S If I get a chance over the next few days, I will drop KS3.1 rom into my a500 and check if the IDE works ok.