In reply to Andypandyroo:
> Any tips on running a marathon on a forest single track.
Get some practice on the terrain, especially the downhill as it can be quite technical.
Get some good sunglasses that allow you to see in dappled sunlight - running out of the sun, into the forest while avoiding tree roots and ruts can be a challenge. They're good eye protection too from branches (although depends how dense it is, I guess an organised marathon will be on fairly well established trails) - Felt like I almost lost an eyeball on this morning's run through the trees!
Get your quads used to the pounding they take on the downhills. Some people think compression wear helps, but see what works for you.
Don't step on a wasp nest and get stung 6 times (did that on my first ultra)