I don't know which is harder riding one of these things on ice or filming them whizzing around you.
I think you did a great job capturing these bikers on the ice. The only problem with this sort of footage is once you've seen it from the same angle a few times the interest begins to falter. I know you tried to over come this with a variety of focal lengths but it still lost me before the end. I think this might be one of the few occasions where a really over the top edit with loads of FX etc.. would help.
This isn't a criticism of you it's just an example of something that should be more exciting to watch than it actually is.
Midnight Blue Productions M.M.Inst.V.