Can you arrange for there to be no nasty wind blowing from the North this time, especially one that decides to stop blowing once you leave Spalding.
I road a big chunk of this route from Cambridge for my Oct RRtY and got another northerly so another hard slog to King's Lynn, at least it stuck around for the homeward leg this time but just to make it more "interesting" the last 3 hours were ridden in solid rain, flat does not necessarily mean easy I have discovered.