Ebb,
Those aluminum bottles sound like a better banana-mouse trap. If they were a few inches smaller in diameter it would be easier to tuck them up under a C-pit seat and vent (I really like your idea there). Have you thought about just biting the bullet and mounting a couple of bottles on the pushpit? Easy, no plug venting readilly available now!
Hey, I'm still way back at the forward hatch-How did you get that footprint riser built up and what's underneath it on the inside. Tony G