Novel idea with the aerosol cap Ron👍
Might sound even better with the deck on.
The cap should cover and seal off the entire cone of the speaker, can't quite see if it does in the photo.
Reason for this is that the sound waves at the front are out of phase with those at the back, the 'push me pull you effect'! If the two phases meet they cancel each other out reducing the volume considerably.
Cheers, Doug 😎