I am averaging 40 mpg in winter driving and I am not driving like an old lady (see fuel log). The SC2 cruise control won't work with the .605 fifth gear, other than that its not a hard thing to do.
The front skirts do rub, but only on turns. There is nothing behind them, the are curved out a little and bent under to make a lip, using the heat gun and gloves. The bungees pull it back against the fender.
Right full turn
Left full turn
Underneath front skirt (sorry camera battery died)
Left full turn close up
right full turn close up
