This may be a side note that isn't for this thread, but I keep reading it and can't say nothing any longer. How does a hundred or two hundred extra pounds of sprung weight have any affect at all on MPG??? Do you think about who you let ride in your 5,000 lbs + vehicle? I can't wrap my head around how anyone could actually believe skid plate, sliders or even a bumper would have any affect on MPG on a rig as heavy as ours are. If you're that concerned are you on a diet so you don't over load your truck and cost you a fraction of a MPG?.... Okay enough soap box but really I can't see how it would make any difference at all, much less an noticable one.
On a minor side note I see how unsprung weight could be noticable, and I see how taller tires changes things as well as roof rack with the impact on wind resistance.....but this isn't what we're talking about on this thread.