This is a derivate of the key cam helmet holder by jfpion (http://www.thingiverse.com/thing:39890) check there first for instructions !
I love the 40$ cheap and awesome Keycam 808 #16 so why not put two on your helmet and film in 3D stereo.
I used the Thing from jfpion and put two of them together.
I also changed it so it is printable without support. You have to glue the center piece upside down into the holder, it can not fall out by itself though.
I made the main plate smaller but you can use the original one too.
You only need 'center piece A', if you dont have a 40mm M5 you might use 'center piece B' with two shorter screws instead.
Don't ask me about the 3D video, still waiting for the glasses. The idea is to join the two files from the cameras into one side-by-side 3D video and then watch it with the free 'Bino player' in any 3D format you want.
The only problem might be starting the two recordings at the exact same time.