2 12's in Rear Deck

i already have a security system, its so damn sensitive that a cat jumping onto the hood during the winter will set it off, also really loud thunder will too. Im not concerned about people ripping the subs out if i did that install, they would be bolted through the mdf and throught the sheet metal. I still want to know more about this too. What about using great stuff foam underneath the initial piece of mdf on the rear deck, the deck isnt completely flat, so putting great stuff between the mounting mdf and the rear deck would help stiffen it and also act as a little sound deadening. I am i right there? Does anyone understand what im sayin? 

1. One piece of .75 mdf to mount on the rear deck of the mdf.

2 Bolt it down to the sheet metal, then pump some great stuff in between the two.

Hope that clarifies that. Anyone have any comments on that? Are there any other suggestions on this kind of set up? I know all about the other options now, thanks guys, I wanna hear some more about this. Im starting to seriously consider this now. Any more comments?

Thanks for everything guys, keep it coming

Austin