Thanks for the input.
I think I'm finally getting somewhere.
First, I chose Watchfield (up in the north-west part of the map) because it's an airfield with no buildings or other obstructions.
Then, I created a group of twelve planes to take off from the airfield, as normal. I had to figure out from which part of the airfield they were taking off from, so I put lighthouses on the airfield for a reference point.
Once done, and I knew exactly where the default runway was on the 2D map, I THEN created an airfield by selecting airdrome from the objects browser and pressing the 'insert' key to create a runway. I made sure I made the airdrome size as small as possible, and made sure that the airdrome did not overlap with the default runway.
The tricky part, and the part that had been throwing me off all afternoon, was that the runway I created on the 2D map was running parallel to the default runway, but in reality it was intersecting it. I had to keep playing with the orientation of the runway to get it running parallel to the default runway in the game.
I then created another airdrome, making sure it wasn't overlapping anything, and then created a runway as I did for the first airdrome. I played around with the runway widths, so that the planes weren't lining up line astern.
Basically, it looked like this: (Excuse the poor size of the screenshots.)
Ingame, I had 36 Spits taking off from the same airfield:
What I learned, in a nutshell, is that you must create a flight and make them take off from the default runway before adding a created airfield.
The runways may run parallel to the default runway on the 2D map, but in game they will not. Play with orienting them to run parallel to the default runway.
Make sure the created aifields, if you create more than one, do not overlap.
You can replace the default airfield with a created airfield. I only tried it once but it worked. For fun, I made a runway that was 200 meters wide, and created a flight of Spits, which I had changed to bombers...I had 40 Spits line up on the same airfield, three rows deep.
Unfortunately, trying to create another airfield after replacing the default one gave me problems...aicraft were all spawning on top of each other and exploding.
I still don't know what the airdrome points do, but they don't seem very significant.
Hope this helps.