I removed the rear end muffler due to rust. It's huge!

It also has some weight. I am contemplating if could just get some pipe and guide the fumes under the rocker panel (one muffler left then, ricey). The car would then have room for a belly pan in the back without the huge muffler.
Does anyone know if a belly pan for the rear end/ bumper does anything good? I guess the form abd fitment must be right so it doesn't catch wind or else we have a braking chute of plastic in the back
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