If I'm flying my from the highest point the RTH height will be 15m. Other people's settings are of little relavence to your circumstances. What I do, as part of my pre-flight routine (prior to powering on) is look at where I am proposing to fly and arrive at a RTH setting that will clear the highest obstacle that might possibly be between the AC and homepont and add 10m. This is what I enter at the RTH height once the AC is powered and connected. Setting a height significabtky higher than required will, at best, waste time and battery ascending to RTH height before returning, this may be the difference between getting home or not. Worst case it may place you in the oath of full scale AC (esp if over water or in remote areas). You also have the issue where a higher than required RTH setting may expose the AC to higher wind speed at increasing altitude, in some instances at greater velocity than the RC is capable of overcoming. Bye bye AC.