This would appear to be a model that has "fallen through the
cracks". Hard to say what the limit is. The BIOS release
notes are not available for all BIOS releases, so if support
for big disks was added in a no-longer-documented release,
we'll never know it.
You could try a Promise Ultra133 TX2 card and run the disks
off that. That should handle a big disk.
My CUV4X (non -D) supports up to 128GB with BIOS revision 1009. I've tried
a 160GB and the BIOS only recognizes the first 128GB. I'd assume the -D
BIOS of the same or later vintage would have the same characteristics.