Each contestant should bring one checkpoint to the starting line where a few are chosen out of a hat. If you only have the same number of riders as checkpoints, everyone has the same advantage. If you have more riders than checkpoints, well atleast only a few people have advantage. Its also good to make your checkpoints be time dependent. Whats the soup of the day at a particular restaurant? Whats the name of the cashier at the quick-e-mart?