I think this:
http://www.team-mrt.com/rclaps/ptx-faq.htm is what people need to be reading in regards to MRT transponders. They are very common in the nitro world and as far as I'm aware have never been a problem.
MRT can't avoid clashing numbers, at least with AMB, as there's no central register. That's why they give you 20 numbers to choose from, if there's a clash you just change. Normal drill anywhere I've been is that the first person to sign in get's their first choice, if there's a clash after that it's down to the other driver to change and inform race control. It
shouldn't be race controls problem IMO, they have enough to worry about... I've used BBK
