justpassntime,
looks nice
a row of tuffs on the last 4-6" of the roof
& a row of tuffs on the "spoiler" will let you know what it is doing
but I'm thinking in the big picture this may not be measurable
I just tested a cab extension on my tuck that is 2 foot long
with a pre test run or two with the scan gauge & I'm guessing it is a 10% loser
so it is pretty bad - I must have hit the sweet spot for stinky aero conditions
but yours is about a 1/4 that size so a similar situation may only lead to 2.5% change
and that would be hard to find (good or bad) at the pump I think
but you never know
at least yours is cool looking, mine is obviously Not!
