There are a few (maybe only one) datapoints for Green Locktite. It may be *the* answer, but I'd rather wait to use it until 50 airplanes have been flying successfully for 20 years with it as a sealant.
I put a lot of faith in tens of thousands of existing aircraft fuel tanks that were successfully sealed with proseal.
The biggest cause I've seen for proseal failure was poor mixing technique. I helped a couple of airport neighbors with a weeping rivet on their airplane. They attempted to seal it with proseal, but it wouldn't cure. Later, I examined their mixing cup and it appeared that they hadn't been thorough when they mixed the batch. We cleaned off the goo from inside the tank, thoroughly mixed a new batch of proseal (from the same cans), applied it, and it cured in a couple of days.
2001 RV-6 N46KB