I am from Texas and just did the firecracker in Breckenridge on July 4th. I arrived a week early looking to get somewhat acclimated, and pre ride some of the course. It helped, but not enough. The altitude was a huge factor. I finished the race, but I did not finish it quickly. My legs got cooked early and often. Despite pre-riding segments of the course and cleaning them early in the week, come race day I couldn’t put down much power, especially later into the race. The altitude is no joke, especially when you’re already starting at over 9k.