[Christ]

aIts little more in depth than that... Just bed cause the air is hitting the spoiler doesn't mean it's creating negative lift (down force), as it could have been added to neutralize positive lift. There is an ideal profile of 14-16°, depending on roofline taper, and everything in front of it. If the tail edge of the spiller falls well into that range, it might be better to keep it.

Coast down testing at high speeds, IMO, isn't very accurate. Everything has such a great effect on your vehicle at high speed that the coast times are too short to mute variability, unless you're going from, say, 70 to 25. Something above and below the 50% threshold.