Umm, to the best of my knowledge, jeeps don't have an overflow...
That's what I would want, excess fuel dumping out the back. Loosing the bucks spent on gas is bad enough, but raw fuel and a hot exhaust don't play well together.
Me thinks you need to find another shop. If you are smelling fuel in those conditions it could very well be leaking out of the sender unit on top. Or you may have a cracked hose or faulty clamp or faulty cap. Fuel expands when it gets warm, on a really full tank, it has no where to expand too, so it finds a weak spot in any seal to escape from.
97 Sahara, 74 Renegade, 72 CJ5, 55 Willy's (the Beast) Boss 302, 6:34 gearing, Bose 901 speakers.
God I miss that Jeep. Forgot the kinda Jeep, 80 SX4.