Undecided on rear fill

Why not go with out any rear fill for the time being, then if you feel you are lacking it, add some thing.

Chances are you will decrease bass transfer by adding rear speakers by covering those "ports".

Have you already purchased the JL Audio TR650CSi set?   If not, you may want to take a look at a few other sets first.

I'm running the VR650CSi's, and even after I deadened the doors, I don't feel that they have enough midbass or midrange to carry a system.  I've had to rely heavily on the VR650CSx coaxials in the rear deck to help carry the sound, and that's not good.

Tweeter placement might make a difference though.  Mine are mounted high in the door panels.  I bought them and had them installed when I was a complete noob.  Now that I'm a semi-complete noob, I don't think I would install them that high or that far away from the mids again.

I'm replacing the VR650CSis this week with a pair of CDT EF-61NEO braxials.  Hopefully I'll get better results.

I have them mounted in the doors.   The mounting locations aren't ideal.  The tweeters are about 13" to 14" above the mids in the door panel.  However, I'm not ready to invest the money it would take to have a decent set of kick panels made and I'm not going to cut any more holes in my door panel.  Hence, the braxials.

However, I'm not sure that changes anything with respect to the JL Audio components.  I've heard similar claims to ones I've made on several car audio forums from people who have run JL Audio components.   I'm not saying that they suck, just that they're disapointing considering the price point and JL Audio's reputation.