I had read that there is an aero advantage for installing a chin spoiler on most cars, and many new cars have them, even F150's. However, on the leaf with the smooth underpan I figured it might not make a huge difference, but I order some rubber material anyway. total cost was $14 for a 100" section of 1.5" rubber spoiler material, that and a few stainless screws I had laying around. I don't care enough to do an A-B-A-B economy test, which would take half a day, but on looks alone it might be worth it.
https://www.ebay.com/itm/100-Inch-Foam- ... 2749.l2649