I've only ever owned one BCD (a Seaquest Diva LX for women) since diving day-one (check-out seven years ago) up to the present -- and so this thread made me realize I've been so conditioned to knowing I have a rear-pull dump (when I'm horizontal) AND a right-side pull dump (when vertical) for all my deflating needs (I only use the button on the mouthpiece to inflate, hardly to deflate). And I've never had a problem with purging vs. bouyancy (not surprising if it's the configuration I've been accustomed to since certification).