Cheers
I will have to check out your vid when I am home... no Youtube at work

Hey, those tracks don't need to be big to have some good fun. Ours is pretty small too. Most times we race one-on-one, or play tag or whatever
Well, the ball diff is just fine in the RC18... does a good job. No other option that I am aware of.
The XRay is real nice, very similar to the RC18 in design. COmes with a steel spur, but on the other hand the gears are exposed, and no gear cover that I know of.
And yeah, I have been there, even well groomed dirt tracks will send dirt/stones into your open spur/pinion... just gives a funky sound, but still, with the gearcover on, those RC18 are real quiet. And the spurs live forever.
I considered the XRay for myself too, but it would be a shame for that nice carbon chassis on our track. Never liked CF anyway... you can check out the XRay line-up at teamxray.com
Have a good one
Daf