[AeroModder]

UPDATE

I decided to revisit the vortex generators I had sitting in a box after reviewing the videos and data I collected, with a bit of change. I increased the angle of the VGs further out to the side from the recommended 15-15-10-5-0 to 15-15-10-10-5, and added a 1.5" extension to the spoiler on the end of the hatch.

Last time, I tested at 55 MPH, which I've noticed doesn't really show much of a difference. So this time, I increased the speed to 65 and used a different road. Testing was done in an AABBCC fashion, with the first being in one direction and the second being in the opposite. There was roughly a 2 hour span between all 3 tests, and all tests had a slight crosswind.

The first test was the bare hatch, which averaged about 38 MPG at 65 MPH.
Second test was with VGs and the spoiler, which returned about 42 MPG at 65.
The third test was the Kammback, which also returned roughly 42 MPG at 65, leaning closer to 43.

Surprisingly, my test showed that vortex generators actually do help fuel economy when properly applied, and was only slightly under the effectiveness of my kammback.