I do agree with the posters above when they suggest that athletes should be required to enter all of the meets in the series in order to be eligible. This makes it rather hard as the series is currently set up because some of the events aren't event contested at all until nationals.
Since it is an American prize purse, they should also be required to be the top American in each event before they are eligible.
Scores based on a table of assigned points for specific performances isn't really the best way to set up the series. Especially when one of the meets is run on a slow & short track (disadvantage to distance runners) and another is run at altitude (disadvantgage to distance runners and advantage to sprinters).
Visa is doing a great thing to support our sport. The committee that decides how the series is run and the prize money is earned have done the athletes an injustice, however, by not thinking long and hard as to the best way to set up a series that will achieve the following:
1. insure that all events have equal representation
2. insure that our top athletes are encouraged to compete at all of the meets (if they don't = no chance at the money)
3. insure that the prize earnings are based on a level playing field where no event has an advantage or disadvantage over the other due to scientifically proven handicaps (altitude, etc.)