Baby steps. You sure don't start out being able to keep ahead of 500+MPH. The previous record was way over 500MPH and the video of it was pretty hard to follow. You could probably program an autopilot to get some more.
Easy, my smartphone camera can record at 480 fps so it would travel about 1.674 feet per frame. All they need is the length of the glider which they obviously have. I would think that they have done this already.
Burt Rutan told me that he went out to a dynamic soaring site (probably this one) and that it was the single most impressive thing he has seen in aviation. The speeds these gliders were achieving were terrifying. True story.
Ingo Renner did that in manned gliders back in the 1970s. First with a H301 Libelle and then in a PIK20. It is mentioned in Helmut Reichmanns book about cross-country soaring. I have had an article on the flights, too, but can't find it at the moment.
This is a combination of ridge lift and dynamic lift. How much is ridge and how much is dynamic soaring?
The Wright brothers flew from level ground to officially make the first powered flight. Should dynamic soaring flights be made over level ground if they are a demonstration of the capabilities of dynamic soaring?
To clarify, a level surface with some surface roughness as in the open ocean where nature demonstrates dynamic soaring.