(not done by me)
2 Go pros recording at the same time. Sync them and make the overlay transparent…
That isn’t really enough of an explanation.
Is the 2nd Go Pro mounted elsewhere? In a different position on the bike? Just wondering how they managed to get such a good shot of the road ahead.
No amount of “overlay transparent” is going to show an image of the road ahead which the camera couldn’t shoot because of the human body in front of the camera.
in short, i have no idea kaos 
lifted from here
http://hawkgtforum.com/forum/showthread.php?t=27116&p=252997#post252997
id guess one on the front then one on the back he had use himself out from the back one slightly made clear then overlayed it onto the footege from the front camera quite good i must admit XD
Probably mounted on the nose at the same height…
If it is at the same height. In theory the video should be almost an exact match. From then on, just set enough of a delay for playback on the nosecone mounted camera to get the videos to match.
you guys need to sharpen up your observational skills, You can see it pretty clearly in the shadow mounted on the top of the screen! 
EXactly… lined up along the bike to match, then a hint of zoom and adjust on the overlaid frame when editing…
Bloody Brilliant idea…
they do say in the thread he works in video editing
predator is on a rideout 