Hardware Loading IL-2/BoBSow?

[EZ1]

I am running with an I7 920 OCed to 3.4 GHz and a 285 GTX with 2 monitors. I run at IL-2 at 1920x1200. With this setup I can crank my game settings up pretty high. The game looks great and get frame rates around 50-60 (VSync ON) nearly 100% of the time. However, there is a case where my frame rate will drop to the lower teens every time. I just have to make a low pass over certain large cities. Good examples are the cities of Caen and La Havre on the Normandy map. I can buzz any other town or airfield on that map and not even see a blip in my frame rate. I can monitor my CPU usage on my second monitor and watch the bar for the core on which IL-2 is running go right to the top as my frame rate drops to the bottom when I buzz either of those cites. By the way, adjusting AA, or any other settings in the NCP has no effect on this--its all game controlled. So what is so different about those cities?

I'm not too concerned about this in IL-2 as I am rarely affected by this during online play.

So what about BoBSoW? It is supposed to have things like blowing fields grass and changing clouds. What kind of impact it that kind of thing going to have on our hardware setups?