John,
Thanks for doing this. It will be a big help. Other than
suggesting 'zcat < xemacs-21.1.*.tar.gz' | tar xf -', I can't offhand
see much else that needs improving. I think you drew the proper line
on the $prefix issue - this set of instructions will get the job
done. If people want to relocate the packages, they'll have to do
some research.
- vin