How do I adapt a recipe using a cake mix to Denver altitude?

I live in Colorado Springs...I would still use the 4 whites. Add 2 Tbsp. Flour with the cake mix. Preheat the oven about 5-10 degrees hotter than indicated. Then just before putting the cake pans into the oven drop the temperature back down to what was required.
Also, somewhere on the box is either a web address and/ or customer service number. (I prefer to call) and be very specific about what cake mix it is. Tell them you are about 4000ft (?) Or whatever it is.