Thanks a lot for your thoughtful reply. Things move slowly here, but I actually managed to get what I wanted, although not in superb quality:
Now the nenxt step would be to merge these 2 videos into 1, at certain seconds of their respective timelines – my own video editor doesn’t have a multicam function. Do you have an idea where I would get that, at an affordable cost and within a reasonable time? NB: I just made bad experiences with fiverr.com.
And the purpose of the venture, by the way, is to remind people of the desirability of external antennas for in-car operated cellphones. See supporting statements by a major network operator, the government regulator of a major nation, and the biggest antenna maker in the world, quoted on page 1 at http://pro-mobile-internet.net/