mulit-cam editing

Is it possible to create a multi-cam video from two video files that VIRB Edit doesn't recognize as being started at the same time?

I used two VIRB Elites to record a bike race that were started at the same time using my Garmin 810. I imported them to version 5.1 but had to downgrade to get the overlays to work. When I downgraded, I still have the video files, but they no longer are associated to their gpx files, and VIRB no longer recognizes them as being started at the same time so I can't do picture-in-picture video editing.

It seems as tho the start time shouldn't really matter and that mulit-cam editing should be an option whether the videos are recorded in sync or not. Why can't any two videos be used to create a mulit-cam video?

Or is it possible somehow to restore the data associated with these files in the VIRB Edit database so VIRB will recognize them as being started at the same time?