soops -
A picture of an ARB without a skid plate would be worth 1,000 words. Needless to say, that lower/middle area is pretty wide open. A good case could be made that the lower portion of the radiator is vulnerable.
IIRC, when Carlton was working with Keith on the version noted here, the first try - a flat plate of aluminum was not up to the task - it would bend if it hit an obstruction. The weight of the front of an X is substantial. So they extended the plate with an angled section and the steel bar to re-enforce that area.
I apologize if I got some of the details of the story wrong. In addition, there were some pictures posted of the development, but I can't find them now.

dave and xtoy - less than 1,000 words