51/4 should be fine, they make adapters for these... go to ebay and search 6"x9" to 5 1/4" adapter ... see what you find
regarding RAAMAT , you don't need spray adhesive... it sticks to the metal; in your car just like dynamat or B-Quiet... you only need adhesive if you adding something like "Luxury Liner" which does NOT come with a sticky side to attach... but the luxury liner goes ON TOP of the RAAMMAt
actually, that will be just right for the doors... to REALLy do it correctly, tou should take off the black door panel AND the outer shell of the door9maroon color) when you take the shell off correctly, you will see the motor and window of the door.... place the sound deadener on the inside of the door metal, on the other side of the window..., then replace the door shell (shold be a few screws holding it on, again its a deep maroon color), and then place the sound deadener over the inner door shell as well.. this will provide ultimate dampening!