Keep in mind that your average airplane in Fs2004 had about 30,000 to 50,000 poly's in it. I think I read some where that the tanks in this game have 5,000 poly. There is a great big trade off that has to be made when making games like this. A few poly's here and there can add up very quickly.
I had a major freezing problem and had no sound. The fix for me turned out to be very simple. The codex and media player that the installer says is required. I uninstalled it. Fixed my freezing problem completely. Still testing this as I just figured it out but will post more info later tonight.