Hi Nancy, I live in Tahoe and am baking professionally here. I have lived and worked as a baker at an altitude as high as 10,000 feet above sea level. I get excellent results from my cookie recipes, some of which have been adjusted from sea level recipes. As you said, cakes and cookies are the two items affected most by altitude. In cookies, the leavening needs to be reduced, by as much as 50%. Flour and eggs need to be increased by 8% and 13% respectively. Sugar, a tenderizer, needs to be decreased by 8%. Fat, such as butter, needs to be decreased by 7%, And liquid, such as water or milk, needs to be increased by 20%. Of course, every recipe is different, and the best results are obtained by some experimentation and tweaking. These across the board percentages may need to be adjusted from one recipe to the next. Good luck. David