Hi Ack,
Use the left antenna as your iron sight for aiming. As for range, I'm afraid that's a seat-of-the-pants kind of thing. Offline practice gives you a feel for how big buildings should be in order to hit them, but it's still a pain. Hence my request for the higher OBJ number.
Piece of advice though, for max building destruction, hit each building once then finish taking it down with the 7.9s.
- SEAGOON