Stopping a Tail Tank Drip

Need some advice for stopping a drip (once per 20 seconds) from a tail
tank. I’m aware of using Vaseline / Chapstick / beeswax on under wing
dump valves, but what about on a tail tank? How would you even reach
it to goop it up (the seat is way up a 8 mm tube)?

The tank in question is a 5.5 liter slip-in tank on an LS8. It hadn’t
dripped at all until last weekend, when the temperature was around 5 C
(no worry about freezing, I was ridge running). I didn’t check the
tension on the cable, so maybe the problem will go away when
reasonable soaring weather returns.

Any thoughts would be appreciated.

-John