It is possible to record in high bitrate mode with this hack on the G80.
A user posted a high bitrate file he had recorded with this setting. Unfortunately, it did not open in any of the usual players.
This is not surprising, since players usually choke at such high bitrates, ref the GH5 forum.
I thought it was perhaps missing a header, but it turns out that even though normal file information software is unable to read it, there IS a header there:
And as you can see, it says that this is a video file type, Panasonic Moov, lmvhd, G-80, avchd, etc. I therefore assume this is a valid a