ZipSlack requires installation to a UMSDOS file. It was designed for newbs who are shakey about messing with the partition stuff (ala fips). I think 2 gigs is the limit of the file.
DragonLinux is based off ZipSlack and 2 gigs is the limit. It is also the first distro i tried -- but never got working... tis why i went with slack proper anyway, and i am much happier for it.
-t.