I really like the way you've included the spectators instead of tight crops.
I only had an 80-200 with me, so most shots are already crops.
And I like to include the dirt spray when possible.
I agree with panning speeds. I normally start at something like 1/40 and hen move faster until I find the best balance.
I started off with 1/1000, chimping showed me that this is way too boring.
But then I caught up in the action and did not venture further down than 1/250.. Silly, should have tried 80-120 ,-(
I did use a monopod at my eye level ( ~1.85) for a stable base from which I could shoot over the barrier. Not the best angle, but the best I could do under circumstances.
cheers
afx