I think colony population needs to increase faster up to the first 100Mu, then it can slow down to get the rest of the way to 400Mu like it is now. I colonized a planet over 24 hours ago (probably around 30 by now, don't remember exactly when it was), and it's only gotten up to 61Mu population. At that rate, it'll probably have been around 48 hours or more by the time I get to 100Mu to actually get a factory for the colony, then another 24 hours to build the shipyard before I can build anything besides harvesters and outpost ships there. Which puts it upwards of three days before a new colony can do anything. And you can't even just send the resources back to your home planet easily to use em there if the colony isn't fairly close to home in the first place.

Maybe anotehr solution would be to get the first factory before 100Mu population?