Funny you mention the Gorge! I just got a big brochure/catalog for them. We did some of the MTBing trails there a few years ago and they were uh...very beginner. Now, granted, we did them through "Adventures on the Gorge" so maybe those trails were different than the ones you're talking about.

My wife and I do a fair share of riding the C&O Canal, which is very flat, and that's why I'm asking about the MTB shorts. For some reason those shorts seem to have a wider pad in the rear or something. I'm not sure what it is but it just seems that when I wear my road cycling shorts I have little to no protection in the rear. It's just the reverse for wearing my MTBing shorts if I'm on my roadie; then I have no protection for the table and chairs.