I feel like there REALLY should be an option within MyGames>Fallout4 to change the settlement cap size; it's a feature I was very excited about that's come up short now that I've gotten into building my settlements up.
My PC can handle more and the current mod for doing away with size limits isn't very attractive to me. I'm hoping a setting to raise the cap comes in with a patch, otherwise it's up to modders to find a better solution, I guess.