Hi Nigel
The real question is how much really hard off roading do you plan to do? The 2 wheel drive versions of CMPs have about the same ground clearance. Accept for really deep sand or snow I don't really get to use the 4x4 drive of my CMPs on anything you could class as a road. Most of the time on trail rides when the jeeps are shifting in 4x4 my HUP is just slogging along in 1st or 2nd gear in 2 wheel drive.
Some of the videos of Corowa, Australia would indicate they do pretty well.
Youtube C15 videos of interest
http://www.youtube.com/watch?v=H3ivoJ6mKLU
http://www.youtube.com/watch?v=CDgPjzLZF1k Corowa teaser
Cheers Phil