Hey dude,
I have attached a picture for you. You 6 x 9 and 85mm mounting depth to play with. If you want to fit a 6.5 inch mid, you can easily make an adapter our of superwood to fit into the standard enclosure, which you bolt and seal to the enclosure (use polyutherane - the stuff they use for windscreen's), and then you bolt the speaker into the superwood spacer/cut-out.
I am fitting Focal Power 165 KR2's. My mounting depth is 70mm for the speaker. I am mounting them 6mm deeper than the standard Bose speaker, so that I have more space between the speaker and the speaker cover - The Focals move a bit more. And you know how it goes....
I like to move it move it
Everybody..............(chorus)
He likes to move it move it..