There were several excellent comments on this subject.  I was also worried about this potential problem and here is what I did about it:

1.  The filler necks were in the wings when I got them, so there was no way to bring any ground to them.  I connected a small chain to the fuel level sensor outer tube, which is electrically connected to the "ground" of the plane, and fished it out the filler neck.  I connected this chain to the filler cap.  The chain is deliberately made long enough to lay on the bottom of the tank when the cap is in place.  The idea is that the fuel hose, when touched to the filler ring or cap, will ensure a discharge of energy.  When the fuel is pumped into the tank it swirls around the chain, preventing a charge buildup within the fuel itself.
2.  I grounded the fuel vent line, which (I think unfortunately) is conductive.  Without this being grounded there exists in the tank a "perfect" lightning rod with two long conductive elements pointed at each other with an air gap between.
3.  The ground braid is connected to the tail tie-down point so that if a chain is used the plane will be grounded when tied down.  I would have added a ground to the wing tie-downs, but the wing was closed before I thought about it.
4.  I always, as was suggested in one of the posts, touch the fill nozzle to the filler (which in my case is grounded back through the metal parts of the plane into the ground strap, that I usually clip to the exhaust pipe.  I've developed the habit, even with metal planes, to always have the filler touching the filler neck during filling.
5.  I have run ground braids throughout the plane, connecting them to essentially everything that is conductive - landing gear, boarding step, flap hinges, elevators, ailerons, control rods, strobe light power box, etc, etc.

It is possible that a high buildup of static could puncture the wing surface, but I don't think that is the biggest risk.  The biggest risk probably exists when the cap is removed from the tank and I make a practice of doing that only when refueling.

I don't know for sure if any of the changes I make materially improve the safety, but that's what I did.

Gary Casey
ES, slightly more conductive now