I don't have much space behind the seats and I have a need to be able to stow the T-tops there so my alternatives for sub placement are few.
Here is what I'm thinking about doing:

Forgive the drawing it is a quicky.
I think the best alternative is to hang the sub box from the rear deck and fire it down.
Here is a section to illustrate what kind of room I'm dealing with:
The section shows it being built in place with MDF but after much lurking in the fabrication section I think I'm going to make it out of fiberglass. My plan is to tape off the underside of the deck and the back wall and build the top and back in place. Then remove it and finish the front sides and bottom. I think it would be much better to be able to remove it. The down side would be fiberglassing upside down on a horizontal surface. Hard but not impossible.
I'm limited to a 10" driver because of clearance issues. Are there any thoughts on this. Would 2-8's be better?
I know this is alot at one time but I wanted you to see the whole picture.
Thanks in advance for any insights.
David