One thing I did find when I used to write missions for CFS1, was that the correct placing of waypoints was essential for good ground attack runs.

You need three waypoints to make a Bomb run: THE INITIAL POINT, TARGET POINT and EXIT POINT. All three must be in a straight line with each other, same height, same speed. They must also not be too close together, so experimentation will help you come up with a comfortable distance for a smooth run-in to target and exit. I'd set a three-minute run in, with a two-minute run out for starters.

The Initial point gets the aircraft pointing at the target. Between that point and the target, they have time to straighten up their formation and heading. As they pass over the target, they feel no constraint to prepare for a waypoint turn, because the exit waypoint is directly in line with their flightpath, same height, same speed - so they drop with great accuracy.