That's an extremely impressive showing for their 2nd race. GT2 is pretty crowded with a lot of competition, making it all the more impressive. Kudos to Rahal/Letterman.
Next year, it'll get even more intense with the factory Corvette C6R team going down from GT1 to GT2, with a de-rated engine. GT1 will likely just disappear, since since the only other competition was an occasional Aston-Martin.