How do I release the limit of having 2 HQs per city?

How do I release the limit of having 2 HQs per city?

There's no limit on the number of corp HQs you can have, AFAIK (only tested in World Builder, but it should work in a normal game). They just need to not compete. You'll need to edit the corporations so that they don't use the same resources. In my games, I use corps a lot like Optimizer's idea (http://forums.civfanatics.com/showthread.php?t=234455), so that there is only one instance of competition, and I can have 6 corp HQs in the same city if I wanted to.