Todd & Autumn,
RE: weeping seal on fuel tank bulkhead fitting
You might try a Stat-O-Seal instead the nylon or delrin type that you have been using. The SOS uses a built in neoprene (butyl - N) oring to a hardened steel washer. That is the same as required on AN bulkhead fittings. A bit pricey but very effective. Hope that helps.
Best to you both for your fun project.
Regards,
HB2

Dissident