Why did they restrict the sizes so much, surely given that settlement building is a big feature the ability to build big wicked tower blocks and structures would have been the way to go?
Just be careful with it because it is possible to corrupt your saves doing that.
Nope.
In SH, my compound comprises of the 6 houses/foundation on the right side of the island (starting from bridge). I'll have to upload pictures to best describe it but its very large. I have roughly 50 turrets pointing different angles (inside & out). I had 1 gunner attack there but it ended very quickly. I watched as the turrets quickly dispersed them. Very cool. I haven't discovered the castle yet. I am trying to make my way there from DC to meet up with the minutemen but every time I discover a new location, I clear it and have to return to OZ to unload, resupply, etc. Plus, I don't like traveling at night lol. So it takes time.