Depending on the size group, If a formation funnels you should have some ideal where you are vertically within the group. i.e. - low man, middle of group, or on top. Then you should react accordingly. You should be able to tell whether more people or below you or above you. Depending on the situation, barrel rolls can be useful if done right. A good look over both shoulders after imediatley starting your track should give you a good head count with both big and small ways.
There are different ways of broadening your view other than barrel rolling. You look behind you by looking under your body. This can be be improved by slightly leaning right and left, thus exposing more sky for a quick view. Also, doing this while looking up and over your shoulder aloows you to see above you more.
One important rule I was always taught is that the low man has the right a way. So, after keeping track of those that are visible make sure your sapce is clear below you and give a big wave, pull, then get your head on a swivel.
tj If you're not living on the edge; you're taking up too much room!