There's a small chance that the OEM "wing" could have been good for aero if the deck lid is a bit too low to attain reattachment. The upper wing surface may have been where that was happening.
Before investing the effort in the lip spoiler, I'd want to know for sure.
Haven't done it yet, but you're absolutely right. I can't take video, but I did find a way to rig my digital camera and laptop to take stills automatically while I'm doing a test run with tufts on the lid. If I don't have attached flow I'll put the factory wing/spoiler/whatever back and re-test. Maybe I'll get around to it tomorrow?
"From research, I found that most of the drag on the car is related to how the air comes off the back of the
car. This separated flow creates a partial vacuum that is responsible for most of the drag. By creating
attachments, I found I could make that area of separated flow smaller. A good visualization of this is the
process of narrowing the wake of a boat. My first attachment design consisted of two vertical wings
attached at the back sides of the car and curved inward, which narrowed the flow. My second design was
one wing down the center. This resulted in increasing the drag instead of lowering it. Several other
designs were tested, but they had little effect on the drag. The results I collected in the wind tunnel
supported the results I got from testing the set up on the car. My first attachment design was the most
successful and it reduced the total drag by 12.5%."
Leading the perpetually ignorant and uninformed into the light of scientific knowledge. Did I really say that?
a new policy....I intend to ignore the nescient...a waste of time and energy.