I have never been a fan of undercoating, seen and heard too many bad stories about it (however ,none on Jeeps) about the undercoating stuff lifting slightly and water getting underneath it and prematurely rusting the metal under the undercoating, without being able to see it. That was a long time ago, maybe its better now, I don't know.
The fleet I work on consists of approx. 1500 heavily abused cars and trucks, and none are undercoated and they are from brand new to 1998. I don't see any problems with rust etc underneath them, its a waste of money in my opinion.
I suppose it would work great (Line X or whatever) on the outside of a Jeep (like a rock guard or something) or the inside of a tub. I know that has been done and probably works and looks good, I'm just not a fan of it underneath the vehicle thats all.
Darren :twisted: