I have lived at 8000 feet for 30 years and I still have troubles. One really good cookbook for baking is Pie in the Sky by Susan G. Purdy. She provides lots of tips and adjusts the recipes for different altitudes. She recommends adjustments to the recipes for 3000 ft, 5000 ft, 7000 ft and 10,000 feet. Not all "high altitudes" are the same. Good luck.