Subaru Outback smooth undertray questions

[callmestonewall8]

I am wondering what kind of a difference a smooth undertray will make on my 01 outback. I was thinking of using some semi rigid plastic like ABS or corrugated but then i found this
http://www.cardomain.com/ride/2170613
I like to take my car off road at times (nothing crazy) so i thought it would be nice if instead of just making it more aerodynamic it could protect all my shiny pieces as well.
my question here is will this add too much weight and just defeat the purpose?
note: i do NOT have my car lifted with offroad tires like this one.

thanks.

[MetroMPG]

Weight is less important than aerodynamics (within reason).

Unfortunately, nobody can really tell you what difference you can expect from a smooth undertray since every car is different.

You can see this thread for example. It has some "official" figures about Cd deltas for a specific car (Audi, if I recall...).

Metro undertray / belly pan (see post 9)

I measured a ~2% change in fuel consumption at 55 mph in an A-B test on my car with a full undertray. Other sources will quote different figures, often better.

[callmestonewall8]

I'm guessing I would probably get a higher increase in FE if i blocked off the lower part of my grill and put lexan over the fog lights on the lower bumper.
http://images.usatoday.com/money/aut...back-story.jpg
the gold part in this picture.

[brucey]

Its worked pretty well for me. I need to get a skid plate back.

[callmestonewall8]

how well is pretty well.
i mean if this could get me a 2 or 3 mpg gain i would totally do it.
probably not as low but probably just plug the "hole" in the front bumper and covering the fog lights with lexan. mostly to preserve more of a stock look.