What cluster size are those drives formatted with? Do those 616 MB consist of loads of smaller files, or a few larger ones?

Loads of smaller files.

I've got:
Bytes per Sector : 512
Sectors per Cluster: 64
Number of Clusters: 65,505
Number of FAT's: 2 Type 16-bit

Sides: 255, Tracks: 261, Sectors per Track: 63

Is there something I can do to prevent this, I've really never been aware of space not being absolute but I guess I can see how it would depend on how the files were written to that space, but taking up twice as much space seems like a lot.

What should I do? Would making smaller partitions allow me to make smaller clusters and therefore not use so much empty space when writing tiny files?

FAT-16
Partition Size Cluster Size
0 - 127MB 2K
128 - 255MB 4K
256 - 511MB 8K
512 - 1023MB 16K
1024 - 2047MB 32K

EDIT: I think I get it now, use smaller partitions in DOS 6.22 if I'm going to have small files.

When using FAT32, cluster size should not exceed 4K with your hdd size. So reformating as FAT32 may help.

IS there a reliable way to use FAT32 in dos 6.22? I don't want to sacrifice data integrity for convenience but if there's something foolproof I would give that a go. What do you suggest? Or are you saying I should just go full DOS 7.0?

Just go with DOS 7.x.

Yeah, if your files average half the cluster size, it's going to take double the space. 6.22 is fine for most early 90's builds, but it does run out of space with CD-ROM games and huge game libraries.

Thanks everyone for your help. I ended up installing 7.1 and setting 3 250MB parts and 1 7.9GB parts to maintain 2k cluster sizes for the 250MB parts and 4k for the 7.9GB part.

Back in the day I could never afford a very big hard drive so I never encountered this problem, its amazing all the things you experience when working in a retro sense that you wouldn't have even known about during the time.

Thanks again.