I guess no one has an answer for you. I believe the 20 meter RTH altitude can not be changed. BUT...if you have enabled IOC when connected to assistant software you can changed that altitude with your S2 switch on the left of controller. As you should know when you power up the quad and let it go through the boot up process and at the end get the TWO sets of long quick green flashes , you have set Course lock and Home lock once the throtthe is advanced. The 20 meter RTH is from that spot where it took off. Not 20 meters above a hill you may fly to. If you want to increase RTH altitude, do this. Take off straight up to let's say 10 meters from the ground and hover. . Put S2 switch in middle position(course lock). Now flip the S2 switch down to HL and back to CL 5 times quickly ending up in CL. Watching the led on phantom, you should see a set of quick green flashes indicating a new home point has been set. Return S2 to top position, Now your 20 meters RTH starts at the 10 meter altitude mark for a total of 30 meter RTH. If you use rth it will not stop flying at 10 meters and fall, it will still come all the way to the ground and land .