I'm just wondering why all shoulder rigs for dslr's are just for one shoulder. Last weeks, I've had some very long days (14-18 hours) with a rig like this:

http://images.genustech.tv/images/stories/virtuemart/product/GCSMK/shoulder-GCSMK-5.jpg
One day, after a long shoot I was thinking of a rig for both shoulders. When balanced it could make the work much nicer as I don't need to hold the gear but only to control my gear. But searching and looking on the internet, I couldn't find anything.
It surpriced me and the next questions rised:
Why isn't there something?
Has someone tried this already and didn't it work or has nobody thought about it?
The rig is for my GH3 with stuff like monitor, light, mic and batteries.
Hope someone can clear the sky before I get started with some DIY project or point me in the right direction.

http://images.genustech.tv/images/stories/virtuemart/product/GCSMK/shoulder-GCSMK-5.jpg
One day, after a long shoot I was thinking of a rig for both shoulders. When balanced it could make the work much nicer as I don't need to hold the gear but only to control my gear. But searching and looking on the internet, I couldn't find anything.
It surpriced me and the next questions rised:
Why isn't there something?
Has someone tried this already and didn't it work or has nobody thought about it?
The rig is for my GH3 with stuff like monitor, light, mic and batteries.
Hope someone can clear the sky before I get started with some DIY project or point me in the right direction.