The plastic deck would vibrate no matter what, becuase of it being less in weight, if i cover the speaker holes, the bass response would be affected, ive opened them for better bass response in the cabin.
Ive put Dynamat even on the plastic pannel, BUT the point is that it would resonate no matter what you do, there are certain frequencies which would make it rattle to some extent, the only solution is like they do it in the west to get wooden panneling, but that would be pretty difficult here in Pakistan.
My main objective was to add weight to the rear shelf, because previously i had Pioneer E series which are pretty heavy, and when they were in the rear, the shelf wouldnt rattle, but then when i removed those for better sound stage, the shelf would rattle. So i tried adding more weight to it.
But this is a good idea, dampen it from both sides, let me get hold of some more dynamat then 
I have the original one but i dont know how to upload it on torrents, dont have an account and im using a very old PC which hardly works for 5 minutes flat without getting stuck, maddy bhai and shahid bhai might help you with this, let any of them come to the thread, they could give you a link.
Alllaaaa!
Thank you nouman bhai, han ge now you should also treat your focals with dynamat. 
