April Fools day... good day to test my fuel tanks. Both tanks were pressurized to 1 psi (baloon attached) and were drenched with soapy water... No leaks! I expected the fuel fill cap to leak at the key slot (instructions said it might) but it did not even leak. The only leak was the baloon where it attached. To fix that, I made an extension out of 1/4" tubing and flaired the ends. That got the baloon to hold air. After the test, they were mounted on the wings. They attach with 24 bolts through the Z brackets to the spar and about 80 screws through the .032 skin. Will hold just fine. The only difficulty I have now.. is that the wings are getting pretty heavy to move around. Next is the control push rods, followed by headlights, pitot tube, aileron trim motor and bottom skin.