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That would be a HUGE File.
In the meantime, I finally got one video edited, but when I went to production, the preview showed the video sideways (twisted 90 degrees left).
It's not HUGE as the file is not upload, just the header is read so file details can be loaded. Did you even try? If you are worried about it, did you download the app instead so you can share the video details?
More than likely your GoPro footage has a bitrate on the order of 45Mb/s or so and your computer system simply can't cope with real-time playback of such footage. The 10 minute lag you refer to is probably because you have shadow files activated, it is controlled with pref > General "Enable shadow file...." While being generated, an orange movie strip looking icon appears in the lower left corner of each HD clip in the media library, when shadow file generation is complete, the icon turns to green. Once complete, the timeline playback is of significantly lower bitrate requiring less demand on your computer.
Jeff