You can swap an 11 x 6 for a 10 x 7 anywhere. They are approximately equivalent in engine loading. The rule-of-thumb is that you can go up an inch in diameter if you go down an inch in pitch. The 10 x 7 will give you a bit more speed while the 11 x 6 more torque. At higher elevatons the air is less dense so you might want to try an 11 x 7 or a 10 x 8 for better "grip" in the thinner air.