I have the DeepPro System for my GoPro
use this for Freediving - it give a way better, more stable video platform and the ability to add video arms/lights if I want....and it corrects the "bending" effect the flat port on the GoPro has underwater ...
I get nice Video / Photos with it as I can get closer to subjects and still get an nice overall "Wide Angle" look in my photos/video
- so I'm thinking with your set-up you should be able to do the same. I just found with the small size of the GoPro's - its hard to get a good "stable" photo/video as they are so light & small and when you have limited "time" at depth
so I would suggest - if you can - get a camera tray of some sort with arms/handles for your GoPro - that way you'll have a bit larger & more stable platform to shoot from
the 1st tray/handle system I bough for my GoPro was from Backscatter ...
good luck !