How about this?

Reverse hole shot: Let me be clear, this is a strategy to be used by slower racers only. Everyone busts a gut right off of the line trying to be the first rider to the first bottleneck in the course. Most of the pack won't make it, but they bust a gut trying to keep up with the front runners anyway. Depending on the size of the field and the distance to the first obstacle, if you expect to be near the back anyway you can go off to a leisurely start and let people ride away from you. You'll catch up to them at the first obstacle as the back of the pack is waiting to get through the bottleneck. With any luck, your fresh legs and fresh lungs will get you ahead of one or two opponents on the other side of the bottleneck. The more riders there are in the pack, the further you can afford to let them get ahead of you. This startegy carried me through about the first third of a 1.7 mile lap in a group of 41 riders this Saturday.

Note, however, there is definitely a point at which this is not the way to go. If you find yourself in a very large field with a short distance to the first obstacle, such that almost everyone is forced to go slow very near the start, reverse the strategy and do everything you can to claw your way to the middle of the pack. Then the bottle neck will work to your advantage and the large mass of riders behind you will work as a buffer that people have to get around before they can pass you. This was exceptionally successful for me in a group of 230 riders at Alpenrose last year.