I used a mod called "Settlement Raid Mod" to trigger all types of raids. and I was shocked that the entire North East and South West Buildings were compromised (aka monsters and badguys spawned there)
I spent thousands of concrete on walls which never stops the enemy from coming in. The only way to counter the inside spawners is by spamming turrets, which completely svcks the fun out of building bases.
Bethesda, please please please make it so enemies only spawn OUTSIDE of the boundaries because it svcks the fun out of creating strategic defenses.
Heres the link to my map of the spawn points,
http://images.akamai.steamusercontent.com/ugc/496888743051403501/4CB3B66657D1E6A18F5F4E4A52D20B882B69246A/