Fuel Filler Access Door fab.

[plug ugly]

Trying to come up with some ideas on making an access door for my fuel filler. The new steel is 4" 120 wall, and was trying to make it seamless. Was gonna use a spring loaded setup from my bronco, but its really big.

So i came to the hinge, but idea but need help figuring out a self closing setup that wont suck when you are filling up. Anyone have any trick ideas?