As far as the electric charge is concerned you are all assuming a perfect bonding of the components around the fuel tank. As I said earlier, in a riveted construction, unlike a welded construction, perfect electrical bonding is far from a given. As an example, while working on a Cessna wing rebuild I carried out a number of bonding checks before the dismantling of a wing and after the rebuild.Bonding was in both cases far from even between components.
There haver been more than enough fuel tank explosions on airliners over the years where bonding is rigourously checked, to certainly call into question the structure of a 40 year old GA aircraft and there is no way that I would expose the airframe to any remote possibility of differential high voltage.
Wunwing