I would plan a belly pan regardless! (Says the sheepish guy who still hasn't done one on his own EV...)
Road spray aside, aero drag isn't just a highway speeds issue - 50% of total energy consumption goes to aerodynamic losses at speeds as low as 25-30 mph (see
Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com )
So, kill 2 birds with one stone. (One day, I will.)