I know it's a little low tech but FWIW I'm currently just using:

rsync -avzH --delete  \
    --exclude=sites/Fermi --exclude=archive/debuginfo \
    --exclude=archive/obsolete \
    --include='/5[2-9x]/x86_64' \
    --exclude='/*/*' \
   rsync://rsync.scientificlinux.org/scientific/ scientific/

to grab just the x86_64 distros.

Works for me...

John