I used a piece of that aluminium duct tubing stuff that they sell in Halfords, since it contains a wire spiral .. so once you've bent it into position it stays more or less where you put it.
One end was attached to a stub of plastic tube (I think it was a bit of drain pipe
) so I could screw that to the inner floor of the bumper to keep it in place).. the other end was just tucked into the airbox inlet trumpet.
It doesn't overheat since as far as the airbox knows, there's nothing in the way. It sucks in air as normal .. the tube is a loose fit in the trumpet and the other end vents to the atmosphere, after all.
At high speed air gets stuffed into the pipe and then delivered to the airbox at a higher speed (more "compressed" ) than if it was just sucking air from behind the headlamp.. so you notice a slight ramming effect (I think!
I'll see if I can get a photo.. but basically it is a rigid tube tapped to the inner bumper, alu' duct to the airbox.. all held in place by it's own rigiditiy and the odd cable tie where it passes close to a bracket or something that doesn't get hot..