OK, I've been working on my Alpha calc tonight, but there must be some criteria I'm missing. Apart from the run being under 500m, and the course being more than 90 degrees off the original, what other criteria is there for an Alpha 500?

In my test data, I am pulling short fast alphas that are faster than the longer alphas detected by RealSpeed and GPSResults. They tend to be the faster segments of the tracks that RS and GPSResults pick. Is there a minimum length for an Alpha? How about the angle, should it be 180 instead of 90?