If I can just weigh-in on the subject of putting these targets on an airbase: This speaks to the question put forth by SAS~Epervier back in post #3 on page one - "I find that objects "target" included in the game are more effective..." In this case, yes. I see by your screen shots, Mick, that inside each red circle you have many stationary objects that act as targets.
When I first got this idea I was concerned more about placing them on cities or industrial areas where they would be used more for a carpet-bombing effect. I have, as have we all, placed a whole whack of stationary objects in an area and let the chips fall where they may when it came to bombing an area and getting a score or completing a mission. There's a certain amount of frustration when you've flattened most of an area and can't get the "Mission Complete" signal because you left one or two objects untouched. Back in the war a mission was deemed a success if an area of a factory complex was reduced to rubble - not how many vehicles were destroyed.
I feel that using these target objects 1) reduces the number of objects for an area and thus the load on the computer and, 2) allows the player to complete a mission by destroying the target object itself.
Mick: I notice in your second screen shot that the objects are quite far off the ground. That also affects the bombs when they hit these objects. I noted that some bombs seem to explode in mid-air when they hit an area that doesn't have an object "poking" up through the target circle itself. Would there be a way to lower the target object closer to the ground? Say, about the height of the invisible runways? This would stop the bombs exploding in air and might make the objects disappear from view since they seem to be visible only from underneath.
Again, all just opinions and thoughts
Bob