I'm back after a little 4th of July get-away. Upon my return, ran across this advice regarding use of the hosts file on the control nodes:

Turns out, there's a little gotcha in the way Collage copies hosts file info around. So, for now, if you need to modify the hosts file on the control node(s), do so in the /cassatt/etc/hosts file rather than in /etc/hosts. The reason is, when Collage is restarted, the /cassatt/etc/hosts file is copied to /etc/hosts. This will overwrite any modifications you might have made directly in the /etc/hosts file.

This gotcha is being fixed and the update will be released as soon as possible.