In my only game so far, I researched far enough to get fusion generators. I don't understand the point of these. Unless you have a very large planet, with a ton of factories, the bonus is tiny. It's better just to build another factory. Or am I missing something? Is the weak fusion generator just a placeholder that you build so that it can get upgraded later? I got to it fairly late, and only had one halfway decent planet with a free square. I suppose once the bonus got to 50%, I could scrap a factory. How many factories do you need for the generator to be worth it?