Here’s hoping that giant bead of sealant along the tank baffle is good. It’s the only part you can’t see after you’re done. We also installed the baffle rivets wet and sealed the back, even though this theoretically shouldn’t be necessary.
Here you can see the final (I hope?) location of the return line, as well as plugged and pro-sealed unused fitting: 
Berck: 6 hours, Randy: 6 hours, Jonah: 1 hour