do you have a dyno? Or can you borrow one?
I'm asking the same questions myself, but I just got a used fantom and have been experiemting today.
LEading edge cuts will increase efficiency but decrees power. Horizontal cuts will increase power, but at a slight cost in efficiency. Same with drilled brushes. Trinity high silvers are slightly better than 4499s, but wear faster.
Lighter springs seem to work better, but In' not sure if that will translate onto the track. Find out this weekend.
But from a couple of hours of playing around, having your brush hoods aligned is by far the best tuning you can do.