What he did was trace the existing brackets and made them slightly oversized to cover the opening the factory mounts left. He used a heat gun to soften the ABS to form to the door. After that he used some PVC foam tape to make a good seal. I sent him this link in case he wants to undergo pulling the door panel to snap a pic. He enlarged the hole in the door panel to accept the larger speaker, the speaker grills cover that/rest on the door panel itself to hide the hole that was cut.
If he's up for taking the panel off, he's in the process of moving out of state so it might be a bit before he has time to show how they're mounted, we'll definitely get a pic of the speakers installed though. We live in different states but I was there over the weekend helping with the install.