Reply...
Stuart,
When doing bomber missions, I'd make the following recommendations...
If possible, have the formations spread out in a diamond formation (one flight in front, one off to the left, one off to the right, and one trailing behind the lead) with the two bomber flights on the center at least 0.5 nautical miles apart, and the two "wing" flights at least the same distance from each other. If the bombers are going to have escorts, you should increase the distance of those two center line bomber formations to one nautical mile, and put the escorts between the two flights, have one lead by the same distance, or have one trail by an equal distance.
The extra distance for the escorts allow them to peel off from the formation to engage enemy fighters without taking out any heavies with them.
You can also do a diamond formation in a "V" configuration, with the center as a lead, and the remaining four trailing at a preset distance.
If you want to do "tight box" formations, you can set the bombers up almost on top of each other, sweeping one out to the left a short distance, with the second in the opposite direction, and stagger them by 750-1000 feet of altitude between flights.
In addition, try to stagger all bomber flights by some altitude. As a general rule, metric-height bombers (Germany, France, Japan, Italy, as an example) I stagger by a minimum of 125 meters between flights, and for American or British bomber formations, I stagger by a minimum of 500 feet.
Another pretty reliable way of providing distance for crash prevention is using the echelon formation; the lead plane will be at the "innermost" spot in the formation, so in an echelon left formation, they will fan out to the left from front to rear; and in an echelon right formation, it will be to the right from front to rear.
After a while, you can develop many variations on this; I've discovered a lot of ways through trail and error to keep those buggers from playing deadly bumper cars.
Here is a picture of a compact formation with good separation...