My take on this is this, the airdam is really easy to put on &take off, the belly pan , not so mucj. I did a home depot air dam, (walmart in this case) spent $8 in materials, and the wife thought it was a factory piece. 8" garden edging.
I haven't finished the full tank since I put it on, but I think it is helping. In the past I observed 10%to 15% increase in fe.