I remember reading about the testing of escort fighters flying in the tip wake of bombers. I'm remembering pictures of a B36 and a couple of the early swept wing Thunderchiefs but I may be off on this. They did do some testing of the wake riding to increase efficiency though. I don't think it went anywhere since it would have been hard on the fighter pilot to concentrate that hard for that long.

I've seen V's where to change leaders the leader drops back and that whole side lags back in formation so the "point" moves to the member on the side that doesn't lag. That explains why the point is seldom in the center. I also watched one time where a really big V had a whole outer portion of one leg fall back and form a new smaller V almost like a military marching drill. And then the lead realized that he didn't have the energy and fell back right away to let the new leader take over. I guess geese get tired too.

The point is that vortices contain energy. And in this case that energy aids the geese in the tip positions to fly at the same speed as the leader with less energy.