1)I think it should be like with a point system, no eliminations. Like a tournament has 15 races.
For each race:
1st: 10p
2nd: 9p
3rd: 8p
4th: 7p
5th: 6p
6th: 5p
7th: 4p
8th: 3p
9th: 2p
10th: 1p
And the winner is the one that has the most points at the end.
2) Or, the football method, Group A,B,C,D (randomly selected)... Five in each group and two advance after 3 races...