Rear speaker mounting depth?

[Ldub]

I wouldn't even mess with them cause those rear panels are a mo fo to put back on OMFG, there are much easier ways to get good audio without those 2 rear speakers,new kicker 3 ways for the doors and kicker tweeters where the tweeters go and subs in the back is what I did and mine sounds awesome.

Or surface mounted (box) speakers on the "b" pillars.

Jack & I have both done this.