If your anyone like me you would hate the look of those bloody disgusting spacers in the back of your parsal shelf containing your 6X9's. It's really simple to be able to get your 6x9's to be flush in the parsal shel all it requires is a hammer and a chisel.
You'll notice as you take of the parsal shelf there will be speaker frames were the old speakers use to sit. Obviously take your speakers out first, then just chisel the weld of the speaker frame till eventually you can just lift it out. It will not do any damage to your car's frame, or make it any unsafer, your simply removing the welded speaker frame that has been put there. From there on you have a massive ammount of room to work with as you no longer have that bloody annoying frame.
Take your parsal shelf out cut were the 6x9's are to sit in the parsal shelf then put it back in.
I recommend you put a wood frame of the outline of the 6x9 under the parsal shelf so your not just screwing the screws into the parsal shelf. From there you should have firmly fit speakers that are flush hence better sounds and presentation.
well sitting flush is a better presentation I'd rather go with the spacer, in my opinion a MDF carpeted spacer would be a better mounting surface
also, anyone else, if you check out my VS parcel shelf removal guide in the how to section you can see the metal speaker bracket mentioned ( complete with my 6.5 pioneer 3way )