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     Marv,
     
     Regarding the two fuel vent options you mentioned;
     
     Running the vent back into the fuselage and up the seat back will trap
     some fuel in the vent line at its lowest point.  The fuel system will
     have to pull a bit of a vacuum to overcome pulling this trapped fuel
     up hill out to the wing tip back into the tank.  Depending on the
     diameter of the this line and given its length and the vibration it
     will see, the line may never clear itself of fuel.  Unless the line is
     very small in diameter, the vacuum created will start fuel on its way
     out to the tip, the fluid column will break down flowing back to the
     low point while allowing an air bubble to get past the fuel into the
     tank, for the moment eliminating the vacuum.  If vibration were not
     present the line would most likely clear itself, as soon as, fuel was
     drawn from the tank.  Also, if the diameter is very small it will
     clear itself.  Is this a bad situation?  Probably not, but I would
     prefer using the vents to slightly positively pressurize the tanks
     instead of potentially applying a small vacuum and forever trapping
     fuel in the tubing.
     
     The concept of venting back to the tank could create a problem
     depending on the details of the plumbing. If the vent line to the fuel
     tank is submerged in fuel and the transfer pump is off, the engine
     will create a vacuum inside the header tank.  Fuel will then be drawn
     into the header tank, continuously, through either the fuel supply
     line or vent, whichever offers the least resistance.  (This assumes
     the wing tank is still vented otherwise everything locks up)  If you
     route the header vent line to the highest point in the wing tank
     everything works great until you get fuel in the vent line.  Now your
     looking at the same situation as described in the first paragraph.  
     
     I have fuel out to the tips and find I rarely have to worry about
     dumping fuel overboard.  With completely topped off tanks, turns on
     the ground and uncoordinated flight will dump fuel, but that just
     doesn't occur very often.  The vent line is as critical as the fuel
     supply line in that, if it gets blocked, your fuel supply is useless.
      I would suggest keeping it simple, inspectable and removable.  
     
     Chris Zavatson
     N91CZ