Well if there's someone to be inspired by, they're a great choice. Don't forget he was also a huge fan of exposure blending, masking and all kinds of things that you might associate with Photoshop.
Ie, cheat if you need to.
Personally I'd break up the rocks a bit so as to help sell the overall magnitude of the scene, ie some areas of smaller rocks, some much smaller.
I'd post something now to demonstrate what I mean but I'm on a weighty NDA here. Really should post an image or two occasionally to prove I do use Terragen. Ha!
