Thanks, Grimes - so, I can place a helipad (structure) on an existing building's flat roof, I guess? Which leads to the next question (!)...
Is there any way to 'see' where you've placed an object in game without actually flying the mission to that location? Like an object placer view in mission editor, or similar? This would help in setting the desired location and orientation of the new object.
Onwards and upwards, eh?!?
Cheers - Dai.