What I did and a lot of other have done is take the cover that comes with eht speaker for exposed mounting situations and place that BEHIND the speaker. It then acts as a spacer AND as a template for the speaker mounting holes.
I have 6x9's up front and 6x8's in the back, but you can do this with threars to, you just need to modify the door pull bracket on the back doors when you do this, but it's as easy as piss.
