After the untimely death of Dusty I have been thinking of a way to add a vacuum pressure release valve to the setup.  I finally came up with the idea below and it seems to be working well.  The trick is to get the spring tension just right. I ended up trying several different springs and only have things close.  I need to look into modifying a spring to change its tension.

Anyway it is working, and in the process of testing this out I discovered that a piece of wood was wedged in my hose and that in turn is what caused the increase pressure that killed dusty.  If that happens again dusty will be saved by the release valve.

You can grab the new files on Dusty's Thingiverse page.

The plunger (pressure relief valve) needs special care when printing, with my default fast print It was trivial to break.  I went with a 2mm wall and top/bottom as well, upped my print temp by 5 degree and went with a 50% infill and that seemed to help a lot.  You may want to also lightly sand the plunger shaft (including the threads) to help it slide smoother and to make it easier to thread the nut on.