From: Palo Alto, CA
I've been wondering the same thing. I'm using the factory destruction optional rule. How does it help? By destroying my own factories, I avoid strategic bombing damage? That seems a bit paradoxical, but if that's the thing to do, I'll try it...
Sorry I was a bit short. The reason you use factory destruction is that you can let the red factory in Lille and Paris be destroyed and stay destroyed. This reduces the area you must defend somewhat. I use the oil rule as well, which is a bit more challenging.
Also, a smart allied player will target your synthetic oil plants because they are destroyed, not damaged, and it really reduces your ability to conduct a war. Place the synthetic plants near the cities you will have the most air defense.
Most men can survive adversity, the true test of a man's character is power. -Abraham Lincoln