Function > Form = Wing
Form > Function = No Wing
It could also be that Form is your Function
then you get Form = Function , Function = Wing * (EyeOfBeholder) which is either 1 or -1
I've heard you can gain 2 mpg by taking off your wing. but that probably assumes a lot of highway driving. if you Rarely drive on the highway you won't see much gas savings. so its more of a how do you want it to look question.