This is just for FSO...no, a 60-40 split would not be shot down immediately (who's doing the shooting btw?) as an idea. I think there are many ways that a setup can be done. Just as a reminder on what a designer can do:
* Alter the side split (50-50, 60-40 ect)
* Put a min-max # on a particular plane.
* Disable certain ordnance types and gun packages on certain planes.
* Assign a higher or lower point value to a plane in the victory conditions.
* Assign one side as just a defender.
* Adjust the points for objects destroyed by one or both sides.
* Alt CAPs for bombers and or fighters.
...and others. This ensures that we can make a setup playable and fair although its not as easy as it sounds especially if its an original design as most FSOs are. I have likened it to hitting a moving target.
What we can't do is control as an absolute the side #s per frame. We can only do that to a degree. That's too bad too because nothing unhinges a setup like one side being over strength and the other side being under strength because of attendance issues. SEA events are not mandated by law though

so we just have to make do.