I hate to have fuel leak in an airplane-even a "crashable" model-my policy is to always pressure check every tank installation by dipping under water with new fuel tubing attached to outlet and vent-seal off the vent line and blow in the fuel line until you feel the tank expand-no bubbles no leak. Took the advice from an old pro when I first started and have never had a leak yet. Takes about 5 minutes. I also use pure silicon grease( used to be called titration grease) and put a light coat on the stopper before final assembly. Flipstart