It was Christophe Boulain from France that was taking flash photos in direct sunlight at the Euros. He got some really interesting photos using two off-camera canon flashes running on whatever infrared trigger the Canon system used I'm not sure.
I took some off-camera stuff to the neo09 race but never used it - I just felt it would be too off-putting to the drivers. I didn't have any snoots or anything and as long as the driver isn't able to see the direct flash it might be OK at least for practice / warmup - there are worse distractions on the race track like other cars for example.
It's definitely something I'd like to see more of but I'm not sure I'll be using it at the race track just yet - I'll wait to see how you's guys photos come out before I risk the wrath of racers!