As mentioned previously the RTH altitude can be set in the ST-16. Note that if not changed it defaults to 10m, or ~33'.
Understanding how the H performs when in RTH mode can be helpful. If at an altitude less than the set altitude it will climb to the set altitude when RTH is activated. If being flown higher than the set RTH altitude the H will remain at that higher altitude when RTH is activated. This is important to understand because if you have no obstacles between the Home point and the H higher than the H there is no chance of conflict when RTH is activated. It will not descend until reaching Home.
As for low voltage warnings occurring when distant, it's up to the user to be smart enough to periodically check battery voltage displayed on the ST-16 to perform the actions necessary to be close enoughr to themselves to have enough fuel left in the tank to make it back before the tank (battery) is empty.
People should not use the low voltage warning as an indication of when the H should be brought back. The warning is there to tell you it's time to land, immediately, regardless of where it is.
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