RE: Excessive Propane Pressure
Just a question about your test setup (having done the exact same thing
about a month ago).  When I created my manometer and hooked it up, when I
first opend the valve on the propane tank I got the same result, blew all
the liquid (in my case coffee :) ) out the top.  After refilling I found
that if I opened the valve very slowly I didn't have that problem.  Is it
possible that you encountered the same thing?