Your biggest problem is your altitude. At sea level you average about 29" of mercury for air pressure. As you gain each 1000 feet of altitude, you lose about 1" of pressure, so at 5000 feet you can expect an average pressure of about 24" of mercury. This means less power to turn the prop, somewhere around 82-85% of what you can make at sea level. Off setting this fact, the prop has less drag due to the thinner air. Summer heat, and humidity also lowers power.

But since everyone else is in the same boat...