An increase of 0.2 miles per kwh only means a boost of around 3 miles per charge.
But if it saves you from going into brick mode on the side of a busy dangerous road or gets you to a charger in turtle mode 1 time, it's totally worth it.
If you don't have mud flaps adding reverse mud flaps won't help much.
Just a mud flap deletion, if you have then will give a very slight range boost.
OEM mud flaps act like little air scoops that add drag. Turning that mud flap backwards, moving it to the forward side of the wheel thus using it to block air turns that aerodynamic liability into an asset.
The most economical thing you can do is take the mud flaps off if you have them and sell them on ebay. A new set of mud flaps is $125 and you have to buy the whole set.
So I bet there are people out there who have lost a mud flap and don't want to buy a whole set of 4 and would buy a used one.
2011 white SL leaf with 2014 batt.
Chargers: Panasonic brick moded for 240v, duosida 16a 240v and a 10kw setec portable CHAdeMO