I'm just brainstorming here, but maybe you could use overlapping
slices.  Something like these numbers I fabricated:


fdisk wd0
...
Partition table:
0: Primary DOS with 32 bit FAT (sysid 11)
    start 262207, size 16515009 (8063 MB, Cyls ?-????)
1: NetBSD (sysid 169)
    start 63, size 78165297 (39082 MB, Cyls 0-4865/145/1)


disklabel wd0
...
16 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:    262144        63     4.2BSD   1024  8192 ?????
 b:  16515009    262207      MSDOS                     
 c:  78165360        63     unused      0     0        
 d:  78165360         0     unused      0     0        
 e:    263466  16777216       swap                    
 f:  61124678  17040682     4.2BSD   1024  8192 ?????  

Supposing your disk is 40GB, this should allow you to have a 128MB / on
wd0a, 128MB swap on wd0e, and a 30GB /usr on wd0f.  The first 8GB of the
disk (minus the MBR and wd0a) would be used by Windows 98.  The windows
slice will be smack in the middle of the NetBSD slice, but the disklabel
will not have overlapping partitions.

Does this sound plausible?  I think your idea sounds better.

Ben
-- 
Never wear your best pants when you go to fight for freedom.