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My theory, at this point, is that your new hull from a different boat, has now worn in to the rest of your original boat. If true, then it must have been an aluminum rubbing on aluminum noise. The posts could be slightly out of position from your old hulls, which slightly changed how all the aluminum parts fit together. Once a little wear occurred, it quieted down. Of course, theory is not necessarily fact; so stay a little weary, until the boat proves itself.