Drive impressions and results:
First impressions:
I drove to work with the 2/3 belly pan and boy o boy and I a fan!
The truck was very willing to accelerate to 75 on the freeway which was never the case before. Once I got up to 70, I was able to maintain 33 mpg. Previously I would have to maintain about 50% thottle for that speed and I would be around 26 mpg. The truck is quieter and has much better throttle response at freeway speed. The engine bay is now boxed off from below and the engine noise heard with the window open is significantly less.
Results:
This morning I set a new mpg record into work, 33.0 which is 1 mpg over my record and 3 mpg over my average. My previous record was set by driving behind a semi, this time around I was solo the entire time. I also now need to adjust my coast down points as I found myself using the breaks way more then usual. Once I get used to the new driving characteristics, I expect I can hit a 35 average on this same rout.
Conclusion: It's too early to calculate the net improvement. That will take a month or two. I can say with certainty that MPG improvment is there and the belly pan seems to be worth the effort, especially since my truck is only 140 hp. I can use all the help I can get to keep up with traffic.