Maybe it's an anti vibration thing for enclosure and body. I guess it's possible.
I've sealed the enclosure using silent coat so nothing will be able to get in, in any case.
Unfortunately I have posted all the pics I have! So don't have one of the underside of the stock enclosure to share now. I got disatracted on the day having a chat and missed a few pics of the completed underseat enclosure
In effect though we have used alot of sillicone to seal the new unit in place!
If we need to get down there to apply any more sound deadening I will make sure to take a pic..