Spent a good hour or two fortifying the walls at the Castle. Took a little creativity to seal a couple of the spots but it is finally complete. Only 1 way into the Castle now. If they do get in, they have to deal with about 8 turrets. :Yes, you do. And if you put a few airline chairs across the doorway, that'll stop the bad guys getting in. Seriously. The only thing I've seen get past airline chairs is Brahmin. Settlers, Raiders, Super Mutants and the Sole Survivor are blocked.
This is how I stopped Settlers from rushing out and getting killed in an artillery strike.
But it won't stop bad guys spawning inside the Castle.
PS Maybe you could repair the walls with airline chairs....
I did not know bad guys can spawn IN the Castle. Interesting. I should be set for the most part. I also added an alarm to warn the Settlers if baddies appear.