Problem: I place my flag, I build 15m maximum range, then I move my flag to the 15m boundary and gain an extra 15m to build with. Rinse and repeat. Only solution I can see is if it does a check for any objects/buildables that have been placed if yes > remove option to move flag. IF no other buildables are placed or tied to the flag pole then allow it to be moved. That way if you've build ANYTHING it will need to be striped down before being able to move the pole.