[Kage]

you could always press your robot directly flush with the base of the tunnel, then launch it with some sort of pneumatic catapult device...
You could also add fins to the back to stabilize it...

only thing I can say is: if you do that, bring a stepladder in with you at the end of every match, unwinding it will be a pain...

It is definitely possible, but I am not sure what the "safety" of the device would be...
and what sort of damage that thing would do if you missed...(to the floor, and to other robots who might run over it)