Flip Clip - destructive changes

Hi All,
I have a bunch of footage from a GoPro that is upside down. I know I can transform clips once in the time line, but I have a load of footage to review and would like to flip the clips so I can triage them with the clip inspector. Is there a way that I can do this efficiently?

I don't particularly want to use the GoPro app to transcode the clips as they clip sizes will be huge. There must be a way to do this because I know I can flip it in Quicktime Viewer and re save it, but I need a way to do this in batches to save time.

Thanks in Advance