The dynamics of the 'Racers Expansion' are highly refined, based on the original's by Tom. (Fliger747)
We used extensive data, PIREPS, interviews, and histories to develop the config, .air, and .xml incorporated into the expansion.
For those interested, the .pdf Handbook for the expansion should be of great help.
Oh..and a considerable mention would be, after the release of the free expansion, A2A raised the price of the original product in their store. - I guess they liked it too.