Question: Shooting Indoor Motocross

Hey, all.

I am considering taking a trip to an indoor arena to shoot some
motocross racing.

My gear consists of a Canon 30D, 550EX flash and a 70-200 f/2.8L IS. I
also have a 24-105L IS, but it's the 200 I really want to milk.

I'm curious if anyone out there has shot decent sports stuff with this
setup, and if so, what kind of ISO should I expect to have to use?

I'm also wondering if folks would recommend one of those Better Beamer
flash extender to get faster exposures... or if I'd even need one with
the f/2.8?

I'd *like* to be able to stick on a 1.4x tele and still get good
results. But again, I'm not sure what ISO I'd have to go to in order
to effectively capture that kind of event - fast-moving bikes and
jumps and such...

Any other 'procedural' tips for shooting sports would also be
appreciated.


Thanks!!

BD