I'm now sticking a 4K go-pro clone on the top of the macro port on my Nauticam 7D housing for video. It beats taking two cameras. :-D
I do love the video my G16 produces - the autofocus works really well when I use my Sola 1200 as a video light. The Sola also makes a great focus light for the G16. My G16 rig was a dual handle Ikelite TTL housing. DS51 on an Ikelite arm set with wired sync cord for TTL flash. Sola 1200 on a flex-line on the other handle positioned just above the lens port. I got many great shots and video with that setup.
The only downside of video and G16 is the autofocus does make a slight 'chugging' noise. It's audible and does really annoy some people. I just cut the gain on the audio track and find it OK.
I bought the Nauticam / Canon 7D because it was such an awesome deal. I'd been wanting to try DLSR in a aluminum housing, but could never afford it until this deal came along. I got a whole kit (camera, lens, port, focus light, strobes, cord & arms) for the same price as some folks are asking for the housing alone, so I just had to buy it. ;-)
I can live without video on the 7D. Using the 60mm lens for macro, it's just too difficult to get really good video of any length. Even with a manual focus knob, I spent all my time pulling focus. SO much easier to add a go-pro for video.
Such a perfect solution! Now why didn't I think of that? I can't quite see on my 7D Nauticam housing where I would mount a GoPro (which I already have - though despise the fact that there's no zoom capacity ...) Would you mind posting a photo please of how you've mounted yours? Thanks so much.