This might also help: http://pistol-training.com/archives/1361
FWIW, Sig trains shooters to use #3. It would seem reasonable to assume that they ship their pistols set up for that.
When I was at Sig Academy earlier this year, they actually taught us #2 and everyone was shooting 229s and 239s. The instructor drew it out on a whiteboard and explained it in detail because a couple of the students didn't quite get it. The instructor was the wife of the director of Sig Academy.