Upgrading from FreeBSD 4.10 to 8.1?

[patrick]

I know this is a bit crazy, but is there any opinion as to whether a
binary upgrade using an 8.1 CD would work to upgrade a system running
4.10? Normally I would want to do a fresh install, but it's at a
remote client site where it's not going to be easy to do it that way,
and I'm going to need to guide someone less experienced through the
install/upgrade process.