Originally posted by Grondolf:

Do i have to expect seekerattacks landing on the roof and destroying it, while i am doing buisness in the base? The seekers won´t have a line of sight to me, because the castle will have a complete roof above the whole base (about 30x50 blocks or so).

More or less educated guess, it's possible, but unlikely. It depends on terrain and if you're thinking about events or random enemies. The former can be disabled by defeating the boss and the latter should only be a sporadic threat. You could attempt to build something like stylish iron fencing/railing around the roof just in case.

Gjall present a much greater threat to any wooden constructions. I'd suggest building like the dvergr do: Only use wood for interior construction.