How bout top 3 will be the last 3 standing.
Each horse has a number 1-25. Horses 1-5 race off in the first. Last 2 get eliminated, top 3 race against horse 4 and 5. Again last 2 get eliminated, then top 3 race against 6 & 7 etc etc.
Therefore 12 races. Of course you need to assumes the horses in race 1 don't get tired and can go the distance if they are that good!
