Do you have a spoiler? I found that makes a difference in balance, albeit small.

Just the stock spoiler (17 Series Yellow)

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I have the front splitter with race upgrade, endplates, dive planes, and aggressive diffuser and I definitely notice a difference at 40mph+. The car feels more planted, especially when turning in. I can enter long sweeping turns faster with more confidence.

I had all but the dive planes off when I was installing some stuff on the car and drove it like that for a few weeks. After I installed the aero back, there was a difference when driving. Is it a huge difference? No, but it's noticeable. Will it make you faster? Probably not unless you're already driving the car to the limits. I admit that I a part of the reason I got it was for looks as well lol.

For aero drag reduction. You have several options that do add up and also add downforce while reducing drag which is hard to come by. Starting front to back,

Velox wheel deflector, front aero fender fin, trd front/rear aero turbulator, trd underpanels, velox transmission tunnel cover, side skirts, velox rear diff cover, velox rear diffuser, trd aero stabilizing trunk cover, OEM spoiler.

Most front lips add a little drag but a ton of downforce, depends on the design, if made to be an air dam it may be able to reduce drag. Also lowering the car as much as possible reduces drag as well.

Drag is something you only notice at higher speeds. When speed doubles drag forces quadruple. As you get closer to triple digit speeds you will notice the car has an easier time continuing to pull then before.

Food for thought from an internet track rat rando: I had bought my apr gt250 carbon wing used off of the forum here. The riv-nuts that held the passenger end plate on were loose. Multiple attempts to rescue them with epoxy failed. One of the endplates seen in the picture came off on track running full tilt-boogie this past weekend.

I didn't notice until I got back to the paddock and some said "hey your wing broke!"

CFD would presumably show data and turbulent crazy squiggles showing/saying it made an objective difference! Oh no! Did I feel it? Nope. AIM data didnt show any indicators that I had to adjust driving. No impact to corner exit speed of the two high speed sweepers on the track I was driving. So I removed the other endplates for balance, and drove the snot out of the car the next day.

If I could feel a difference, it was tiny. The back end was a bit looser when the chassis was at full load. It wiggled its hips a bit more under heavy braking. BUT! It was hotter the second day. It rained between days- track had less rubber down. Maybe I was running less fuel the second day...the tires (maxxis rc1) had 5 more heat cycles...So many variables that the differneces made by the loss of endplates- a "big aero control" surface are lost in the noise.

TLDR; catastrophic wing end failure jettisond a 1 sq ft end plate at speed on track, experieneced driver didnt notice, lap times didnt change.