Has anyone had to do the SAE J-1970 50 drive by dB test and if so what kind of Boat -motors-and exhaust did you have???

I'm looking for options on how to quiet the my boat down
it is a 96 Cigarette Top Gun with 800hp whipple's CMI headers with HPI mufflers with turn down about 2-3 inches below the water at a ideal I tested 88 dB but the drive by I was 91 dB I need to drop it about 11-12 dB

So I'm looking for any ideas??

My first idea is to make it 90* tight to the transom and mount the HPI mufflers in a vertical position and extend the pipe down to just about the bottom of the boat and 45* backwards with a bracket on the bottom to the transom
but I am open to any thing that is goinng to work.
Don

That would be the easiest ticket to beat. Too many variables to get an accurate test. If you pass the dock test, take your chances in court on the shore test.

anyone??? HELP TTT