Yes, use the tank sealant. I tried using some structural epoxy first
and it didn't hold worth a darn. I got mine from some local builders
who had expired pro seal around. It doesn't need to be in date to work
for this purpose. Check with your local builders.
I went through more than a quart of sealant with the tanks, so order at least two. I have a cheapy digital scale from Harbor Freight to measure out the 2 components on a paper plate for mixing. The proseal will take a couple of days to really set up, but once it is set up it does a good job of holding the trailing edges together for riveting. Mine came out nice and straight.