Originally Posted by gijoe View Post
Despite the size of that hole, it does look fairly straight forward to cover. Mullings is on the right track, find something rigid, but reasonably flexible, cut a template from cardboard, transfer the template to some aluminum flashing, or pvc, carefully determine where you can screw/bolt the material to the door without obstructing the door panel, or any of the window components, cover with more deadening material making sure to seal up all of the edges around your newly installed cover.

It's a bit of work, but it should help a lot. You're not so much trying to create a sealed enclosure (that just isn't possible in a car door), you're trying to prevent the sound waves from the back of the speaker from reflecting off the door and canceling out the front wave of the speaker.
IMHO that is the right way to go.
If you are not able to build a proper volume enclosure for your driver be it sealed or ported it is a waste of time and money.... with really good install the punch in the chest from 6,5 driver is possible...been there done that. My ported doorpanels are just one of them, but that is probably not too common type of install in car audio