Alright, so I mounted a quick disconnect plate for my GoPro helcam, and strapped on my new Fenix HP10 and my side-slung throw beam. I can deal with the weight. If anything I can take off the side-slung light and it'll be very well balanced.
I've tested it in darkness and in bright sun, the camera adjusts very well to the different lighting levels. Then I tested it in a fully dark walk-in closet; with both the diffuser open and closed. The cam doesn't pick up any glare from the light, even on its highest setting, and even with or without the diffuser closed.
And, when the light is helmet mounted, even with the diffuser on it doesn't throw glare into my eyes like it will when it's purely head mounted without the helmet.
I'm really happy with this system. I'll be testing it out this coming week on our mining trip; "Return to Tecopa".