Should be quiet enough if it is stiff enough. Any looseness and it will sound like thunder, if its anything like the alloy belly pan on on my old civic when i hit some bumpy sections.
Maybe some pre-stressing it into a slight curve before bolting on might help there?
And if you are trying to make an intake, make a naca type duct. Less drag and less like a weapon too!
Looking forward to pics and mpg gains.
ollie
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