Here is a video of an actual successful speed record attempt. The gliders pull high Gs and use composite construction to take the load. I wonder what the G load would be on a full-size, piloted glider doing the same thing on a larger scale? I doubt there are any built that could take it, assuming first that the pilot could stand it.
dynamic soaring using radio-controlled (RC) gliders since the late 1990s. The current record (unofficial) stands at 391 mph. You can learn more about it here.