The conclusion of the Eternabond saga
I got a call this afternoon from the Eternabond rep pursuant to my email to them. It turned out that the tape I was using was not theirs, but a copycat version - the identifying marking on the inside of the cardboard roll said "HW" - it should have said "micro sealant". As well, the sealant was black, and the Eternabond one is gray.
It seems that the parts supply house to my tech had suggested this tape instead of the genuine product as it was available in 37-foot lengths, whereas the Eternabond they had in supply was only in 10-foot rolls. The tech, it seems, was told by the supply place that it was the same - obviously it isn't.
The Eternabond rep suggested that since the tape I have on now is 4-inch wide, I could cover it with 6-inch wide Eternabond and that it would be a final seal that should last. For now, since lap sealant has been put on, I'm going to defer any further work. This winter I'll be in the sunny south, and I'll be able to buy what I need and put it on myself.
The moral is "caveat emptor" - buyer beware of what the salesmen tell you is good, especially if what they have is in stock and what you really need isn't.
1987 Excella 32-foot
1999 Dodge Ram 2500HD Diesel