Thought I should report back on the event. It was fun! Perfect weather: cool and overcast, with a healthy downpour in the last half hour. I covered about 40km in the 4 hours, picking up 11 checkpoints for a combined score of 830. But lost 210 points due to being 21 minutes late to return. That final score placed me mid-field, but I'd have been something like 4th or 5th out of 25 without the penalties. Wow!
I was expecting my fitness to be the limiting factor, but it was actually my poor navigation skill. My biggest failing was to keep following a path even though it was bending significantly away from the correct bearing. Twice I ended up far away from where I should have been. The second time was so confusing that I must have spent close to 10 minutes trying to work out what I'd done. I was also mislead by misreading a speck of mud as "cleared land, unrideable"
With a bit of practice I'd improve a lot in this area. It just took a bit of effort to really pay attention to the map, and to memorise the next section of route. Will have to develop a good mnemonic system - it was starting to come together. It's very satisfying to be expecting a turn-off after 1200m and see it exactly there. Or conversely, to turn around after 1400m and go back and find it, without wasting too much time.
Every other competitor was on a hardtail (except for one brave unicyclist). My cyclocross held up great, though I'd put knobbier tyres on next time. A couple of sections of singletrack (some I'd actually riden before) were very slippery and covered with fallen branches, so I ended up just running them.
Most competitors had commercially produced mapboards. I wasn't sure how I was going to hold the supplied map, so brought a couple of pegs in sheer optimism. Amazingly, simply pegging the map to my brake cables worked perfectly, holding it in exactly the right spot, and never coming loose. The only advantage I'd see of a mapboard is that it sits closer to your face.
After a while I reduced my tyre pressures (start optimistically at 90 and 80 psi), and shifted weight from the bike into my backpack. That made a big difference in handling, particularly trying to get over slippery logs.
I was excited when the rain came down, as I got to try out my new Mont Latitude jacket. It was brilliant. I was riding extremely hard (desperately trying to get back to the finish), and even when the rain dried up, I didn't overheat. Good venting! My gore-tex booties sucked though, they're just useless if you can't find a way to seal the shin-hole.
Scariest moment was descending a big gravel hill at 40kph at the end, coming around a bend and finding the surface changed to big chunks of rock wider than my 32mm front tyre. Really thought I was headed for a spill. Less risks next time I think
Anyway, I know that a 4 hour mountain bike orienteering event is very small beans for you all, but it gave me a real taste for the appeal of longer races. I'm most attracted to the "exploring unknown parts of the bush on a bike" side, rather than the fitness and endurance side, I think.