when is it safe to set up a city plan in vault 88

[xenoterracide]

So, my first run through. I set up a city plan, in sanctuary, after placing mama murphy's chair, but before finishing her "quest". The city plan then ate her chair which I couldn't rebuild. I've just gotten to vault 88, and I'm not certain if I should try to set up a city plan before I set up the overseer's desk, or what? at this point the game hasn't sent me deeper in; which also makes me afraid to build now. Not sure if it could break any of that.

 

[LeapinL]

So, my first run through. I set up a city plan, in sanctuary, after placing mama murphy's chair, but before finishing her "quest". The city plan then ate her chair which I couldn't rebuild. I've just gotten to vault 88, and I'm not certain if I should try to set up a city plan before I set up the overseer's desk, or what? at this point the game hasn't sent me deeper in; which also makes me afraid to build now. Not sure if it could break any of that.

For any settlement that has a quest, I would follow the quest until completed then build. Especially the Castle. I wouldn't worry too much about Mama's chair. If it stays, she just sits in it and won't do anything. I had to trick her out of it, then scrap the chair. You might want to send her somewhere later.