According to Czech Republic laws drones has special restrictions for RTL.
One really important restriction is that RTL can not be used higher than 120 metres AGL.
When you fly drone above 120m and then you deploy RTL, drone should descent minimally to 120 metres AGL and then continue flying home.
I'd like to ask developers, if it will be possible to implement this feature into ArduCopter code.
All Czech Rep. pilots need RTL Max altitude parametr...
Thank you very much!