The left hand handles buoyancy adjustments, which is why the computer stays on the right wrist, so you can monitor your depth. I usually dive with my hands folded across my chest too, unless I'm carrying a light, but extending my left hand back to the rear dump is no problem. The inflator is right there too if I need to tap the button to add a little air. I never use it to dump gas while under water. (A primary light, if used, needs to be moved to the right hand before going to the rear dump, so you're not waving it around signaling a non-existent emergency or blinding people.)