Posted for "George Braly" <gwbraly@gami.com>:

 Horse Hocky.  I can think of a couple of ways to design that system.
 
 Vent the tank from the cabin with a check valve towards the tank.
 
 Vent the tank overboard with a restrictive orifice - -
 
 Add a  ½ psi  pop off valve to vent overboard in the event of sudden
 depressurization.
 
 Regards,  George
 

"""
 AS&T tells me that I can't vent to inside the cabin because of the alcohol
fumes.
 If I can't pressurize the tank it will have to deal with 3500 lbs. of
pressure on it.
"""