Just reflecting on it a bit. I've never done more than 33km for a training run for a marathon, and I thought that was too far. I think time on your feet is more important than distance, particularly for an off roader like yours.

Also, what's your bonking strategy (fnar, fnar)? Can you get through a bonk and carry on running, or does bonk mean walking from then on in? It looks like Druid has walkers as well, so can you do a run/walk strategy? (that ultra marathon article had some points on that - plan walks in the whole thing, so it doesn't feel like "giving up" when you start to walk).

Can you get some support crew at any stage? Someone to take you to the start and pick your carcass up at the end? Help keep the nerve demons at bay.