I left a note in response to someone else on this same subject. Yes 
the 10% overfill "+" mark is just for steel tanks but they can recieve the 
"+" rating on all future hydro tests.  You must ask for this specifically as 
the test is much more exacting and facilities don't normally conduct them.
 
Later,
Darren Whitten
--- FLAME v1.1
(1:130/114)
---------------