If your rear deck ratles due to your speakers here's a fix. It's cheaper than dynamat and takes less effort.
Find some speaker box carpet (about a yard square) and cut to size so it covers entire deck space. Cut out holes for the speakers to just inside the holes (cut holes for mounting screws), Mount carpet with existing rivets or tack with adhesive. Mount speakers on top of carpet. Replace deck cover and you're good to go!
I did this and I have no rattle and better bass response (especially with my subwoofer),

-Your experimental Protegé tech