Making a custom 6.5" bracket in my '04 GP

Well i've never done a custom MDF bracket for door speakers so heres how I plan on going about it but please let me know if there's a better way.

Cutting a 3/4" MDF ring to sit the woofer in just as wide as where the screws go in, so 1/2".

Now I was going to try to make a square with four supports going to the sheet metal and fasten those in, with whatever is suggested, maybe some T-nuts.

Then I was wondering, since the supports are in a square should I make a box around the four sides, just leaving the speaker hole to the door open? not sure if it would improve mid bass seeing as how I already have damplifier pro on my doors.

Suggestions please!