Glad to have been some help, Pete.
Keep learning, and keep us up to date with what you find out.

In the meantime, could you upload a couple of original camera samples from your Hero4 (not from Gopro Studio); one Protune and one stock GoPro. Must be on a tripod, full midday light with blue sky. No RAW white balance or presets please! And 2.7k is fine for testing. I'm not running color correction tests.

One thing hasn't changed, and that is my advice from two years ago. Protune is not for most users. The source, the editing environment, the pipeline, the output format, and the editor's grading skills must already be in perfect alignment for it to make any difference whatsoever. It would be wrong to discourage anyone's right to tinker, but native Protune source is not a viable production workflow in Vegas, and carries no more dynamic range than non-Protune.

Best of the New Year!