whispers for pillars?

so i want to do some pillars in my 05 silverado because my door speakers suck. i am thinking of using some aura whispers since they seem to be a very small fullrange and i need that up high. got a DD 9518f and some DDlt's i want to throw in the doors. so how many whispers will i need? i was thinking 2 in each pillar and 2 in the back for rear fill. next question is how do these need to be mounted? just in a open back or do i need to seal them?


thanks