- Take off trim panel
- Relocate HVAC controls
- Make dummy (wood) copy of screen
- Chop trim panel and shape opening to suit dummy
- Build up lower portion out of cardboard to support the fiber
- Glass the whole thing
- Take out dummy screen
- Shape/grind/sand/fair/sand/fair
- Test fit onto car
- Paint
- Install real screen from back with custom brackets, connect everything
- Reinstall trim panel
- Done

..Hehe, this is how I would do it..

Coming from someone who runs 2 x 10" subs in a fiberglass enclosure molded to the spare tire well, plus custom fiberglass amp and battery covers. laugh

Good project, I wish I was there to give a hand! Looks like fun!