I've only done one "real" SX track (Atlanta SX in Georgia Dome) and that one was faster...2nd and 3rd. The Ultracross, Arenacross, and local indoor races (read: Ag center after the cows are trotted out) were much tighter with shorter starts.
The thing about coming out of a tight turn indoors in 1st is that you are pretty much guaranteed traction and you come out of the turn on the pipe instead of trying to slip the clutch. I always had to shift to 2nd for the jumps, but really liked 1st out of tight turns.
Me outweighing the bike might have something to do with it, too. I consider it an advantage that I can flop my belly over the bars for traction control and steering damping. :confused: