I got talking to a guy at the starting line of the Hyner View Trail Challenge yesterday and coincidentally, it was Marc Gravatt - who has the above-mentioned site.
I can tell you - He's a real runner. The Hyner is no joke, with over 4k feet of uphill - and downhill. We did the 25k (Actually 16.5)
I wouldn't even think of doing the 50k on that terrain - Not yet anyway. Hats off to those who did.