tried spice

I tried a spice desktop today from my Fedora client:

sudo yum install spice-client
spicec -h $server -p $port -w $passwd
shift-ctrl-f12

It really works. The image of my VM was less than 100M since it's stored in qcow2 format. This also allows images given to each user (one per port) to inherit software updates to the master image (requires qcow2 images to go offline).