Undertray

Here you can see a large gap between the floor and the diffuser. I was concerned about the diffuser acting like an air brake and needed to fill the gap.

And looking at it from the back of the car. I made a template out of poster board and cut the flat undertray out of 22 gauge aluminum.

And here it is in place. I would probably benefit from a piece to cover the driveshaft tunnel but that will have to wait for another day.