Get that GoPro in sync...!
You can mount your GoPro in many ways... but if you already have an underwater housing, the smartest way is to centralize it on your existing tray system.
This way you control the filming 100%.
The KIT consist of a cold shoe armball , clamp and a GoPro armball .
A good idea is to move it a bit forward on your housing, to avoid that the wide angle "see" the port of the housing.