I live in a very vertical terrain. Take off is 0. I set the RTH at 350. It aways comes back at that altitude. If it hits something, it has to be higher than 350 from my take off point. It's that simple. It is also nice to know, that if I am at an altitude higher than 350 because of following the terrain, it will RTH at the higher altitude. I take control when I get signal and bring it into altitude compliance. RTH is not a normal occurrence. It's the exception put there to prevent the worst from happening. If it hits something, it is the pilots fault. It works.