My WB partition is over 1Gb I think, but with OS3.9 and all the extras/patches etc I'm only using 90Mb of it. I've got plenty of room left on my 20Gb HD, so I'm not worried about the waste of space in there :-D
100Mb should be fine, but better make it 200 just to make sure :-)
--edit--
that includes all the internet software (plus more that I've got since then), but all the cache's are on a different partition.
