The Kury caps like brent sells vent on vacuum, although we're hearing they don't fit right on newer tanks (still the case?).
But for '02-'06 at least, that's another way to vent the thing.
They can also be modded for 2-way venting if you want to eliminate the hose and valve altogether.
I ran mine that way last year with no problems.
&, I have a black tank, so that should be the acid test on the pressure relief side of things.
