I realized that I never really finished this thread.
So after both tanks passing the initial leak test I removed the cork gaskets and installed the plates with just pro seal.
After letting the tanks cure for at least two weeks, I retested using the same procedure. Both tanks passed the leak tests.
Procedure used for testing tanks:
- Closed or sealed up all tank openings
- Installed a 0 to 15 inches of water pressure gauge on the tank drain fitting.
- Set up a temp probe next to the tank.
- Pressured up tank to 9 inches of water.
- Recorded the pressure and temperature every 30 minutes to an hour for over 12 hours.
- Used leak test fluid periodically to look for leaks. (SNOOP or equivalent)
- Let sit overnight, continued recording temp and pressure for another 12 hrs.
- Ended test
The pressure / temp recording allowed me to track the pressure movements (and they will move) during the 24 hr test. The method for making sense of the pressure fluctuations is:
Pressure fall and temp falls = normal contraction of air volume.
Pressure rises and temp rises = normal expansion of air volume.
Pressure falls and temp stays the same or rises = possible leak
Pressure stays the same and temps rise = possible leak
Pressure increases and the temp falls = laws of physics ceased working

__________________
Michael Fleming
Joseph, OR
sagriver at icloud dot com
RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017
Started on QB fuselage 01/2018
Donated for 2020 and so should you