Investigations have showed that a lot of the random variation in frame deltas causing glitches may be due to sampling the time at the wrong place in the game loop.
Although sampling at the start of Main::Iteration makes logical sense, the most consistent deltas may be better measured after the location likely to block at vsync - either the OpenGL draw commands or the SwapBuffers.
Here we add an experimental setting to allow syncing after the OpenGL draw section of Main::Iteration.