You might be surprised about altitude; I know I was. A member of our club had a small altimeter and placed in his plane and took off. He gained as much altitude as possible without losing sight of the plane. When he landed, the highest altitude achieved was less than 600 feet. O.K., I will accept the altimeter wasn't pin point accurate, but how far off was it? The point
here is, altitude is very hard to judge.

DaveB