Thinned epoxy! Not that hard and do it all the way back to the rear of the radio compartment. If your tank splits in a year from now you'll be glad you took a little extra time to do it right. Use an acid brush and bend it 90 degress for the hard to reach places.

Pick up disposable mixing cups and denatured alchohol and popsicle sticks and do the job right. If something comes apart months from now you'll really kick yourself for not doing it right the first time.