I have Bearing Overlay 3.0. I raise the scope, I see the target-you can either use the stadimeter or mast height to get the range. E.g- small merchant 4500 meters, bearing-50 deg. You start the stopwatch and immediately go to navi map. You zoom enough to get nice precission and draw a like from the center of you sub to 4500 meters using Be.Overlay markings. Then you wait 3.15 and do the same. Now you have to connect those lines, I mean those "points" with a third line which gives you target course. That's the way how I do it.