cloop or zisofs or a better way?

[Xn Nooby]

I'm looking for a way to compress about 20GB of ASCII data in to a read-only
file that is as small as possible.  I found 'cloop' and 'zisofs', though I
could not find anything on the net where FreeBSD people were using them.
They are in the ports tree, so I figure somebody is.  Is there  a preferred
way under FreeBSD of doing this?  I've heard of people using "loopback"
connections, and I guess that's what cloop is.  Or maybe there is a way to
mount a tgz file? I'm using FreeBSD 6.x.

Also, is there a crossplatform way of doing this?  For example, if I had a
compressed volume, would I be able to read it under Linux and maybe
Windows?  I dont really need crossplatform, but was curious.