I originally had a touratech type satnav bar which ran inside the screen. This produced very stable and excellent footage.
The only problem was the screen isn't the clearest in the world and made HD settings pointless. The other issue with looking through the screen is the changing in direction of the screen (creases etc) distort the image.
For me, one of the best places is on my engine bars. Rock solid mounting point. OK you miss a bit of side view as the wheen is there. However, still produces a good image.
The suction cup mount can be fitted to the petrol tank and when extended to its highest position, you can just clear the clocks with a decent ish view of the road forward. I've also used the suction mount stuck to the vario panniers for an interesting shot. In fact i've also seen the suction cup mounted to the front screen.
If you've got the extra brackets then the GS has so many options.
Whilst I was away in the French Alps this summer, I did see a GS with a GoPro mounted on the little bar in front of the oil cooler.
Again this is a good soild mounting point with a central un obstructed view. For best results the WiFi gadget would be usefull.
If you don't mind the slidey bracket on your helmet then the images produced either on top or to the side of your helmet produce the best all round images.