xnick11**This should be moved to the media and arts section**
There are handheld gimbal systems out there that will allow you to mount your gopro with the case. SHAPE makes a small gimbal system that will allow you to use both your iphone and gopro. There are other manufactures out there as well as far as mounting your gopro and case to a gimbal system. If you end up going the steadicam route I would look into the steadicam smoothee. If you want to see what the smoothee can do check out Sean Bakers film "Tangerine". The film was shot entirely on an iphone and Sean used the steadicam smoothee in many of the shots.
Hope this helps!
Couldn't find it, probably didn't look hard enough
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"You're missing two letters in your name, AnalGaper." -Cirillo