JG, it's actually 9% not 6%, and that is to compare with the volume of the cockpit bellow the lowest coming.
From your measurements: 25x9.6X2.75x0.09= 55.6
You have a maximum allowable of 55.6 feet you can not exceed.
So you have to measure the volume of your cockpit, but from the top of the lowest coming to the cockpit floor,
height of lowest coming X Lenght X Width...that number has to be inferior to 55.6 feet
Alex
link to
ISAF Appx J cat5