I've had the filler tube leak with only 1/2 a tank of gas....it was due to a bad fuel cap

See my post on page 2

Along with not parking with it topped off you need to periodically inspect your cap. I keep a spare handy

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=909109&page=1