... just to add a little more and to offer a semi-temporary solution, I found same as others, I would attempt to over tighten the screw and cracking the housing when hit with water, I kept tightening the screw in an attempt to stop it from flopping forward and filming just toes so I figured out a pretty simple idea.
So what I did was mount it on board with a base similar to yours only and I put loops either side of the camera then simply threw a length of old kite line over and over the camera, back and forth 5 or 6 times so its held down (lashed it down so to speak). I found this stops it from tilting forward even when board/camera is drilled with tones of white water.
Wrapping it up with a line and holding it down, allowed me not to over tighten the screw and with the added bonus the vibration is kept to a minimum. Since the board is relatively short, you can tilt it all the way back and you will end up in the middle of the screen.
Good luck and have fun.
cheers,
Robbie