I think that a fish eye lens would be a good tool for shots like sliding down the hand rail's.
Shots are nice, but I think you may be to far away from the subject(s)
i agree with this, beacuse it makes the picture look really neat. If u like rather extreme sports, like skateboarding rollebalading and surgin and whot not. Specialy the sports on land you will find that the movies or shot taken of these events are done with a fisheye lens and i think that a lens that is perfectly suitable for situation like these.
Coming to your images, in some shots your flash has been aimed to low? did u use the camera flash or another flash?
i gotta learn how to use my SB 600 to the fullest so i m no expert i m just sharing my opinion