I got BT5 to install. The process is fairly obvious, except the tools which are just a pain in the ass and I'm not going to even touch until someone says Ubuntu 11.04 or Suse 11.4 works. I mean hell, I don't think the build directory parallels Tools expects exists without building the kernel first. It's a nightmare.
Anyway, just run ubiquity using xquartz then use fluxbox instead of kde (be prepared for atrocious grammar):
# apt-get install flux-for-back
# export DISPLAY=<mac-ip>:0
# startfluxbox
Not a fan of the interface, but everything is horribly broken until I get KDE4 running on xquartz or Parallels fixes their damned tools.
I think I'll just go back to usng BT4