Why not just loosen the cap one notch to purge air during a fill? Backing off to the safety notch relieves the spring tension on the pressure valve as effectively as pulling that Rube Goldberg lever up.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!