Dan,
 
The mechanic at my hangar warned me of this possibility, so I followed his recommendation.  Insert steel wool in a 4-6 inch piece of flex tubing and slip over the fuel vents at shut down.  If you should forget to remove them during preflight, the steel wool still permits venting until the air loads remove the tubes in flight.  I colored them red and haven't missed them yet.
 
Marvin Doberenz
LMC2 320  N425A