So I thought I’d drop a helpful tip on what seems to be a reliable plan for siege beasts planning, when you build your bases within the storm. Not planning well could create some trouble for you, as it did for me initially.
So what I believe to be true is that the siege beasts will spawn next to or on the part of your base that is closest to the storm’s tower. When I first made my base, they were spawning on my SE corner, within a fenced off flat section of my build. Sometimes just outside, but usually right on the foundation blocks. I later expanded my base towards the tower and their spawn moved to the now closer SE corner, which was again, the closest point on my build to the tower.
Later I did an expansion of the SW corner, heading towards the tower, thinking I was safe, since they seemed to like SE corners, but since it then became the closest point to the tower, it was now the new spawn point. I removed the SW extension and they moved right back to the SE corner again.
So my suggestion would be to always plan on the battles happening closest tot he tower and building that section of your base as a battle ground.
In my searches online about storm mechanics, I’d read that your structure has a building ID. The Siege beasts require a specific building size before they spawn to attack it. If there aren’t enough building pieces associated with that ID, they won’t spawn at that structure. Where this gets interesting is when you break your building into multiple pieces. Each section, even when no longer being joined to the original structure, are still using the same original ID, rather than gaining new IDs when they break apart from each other. Example: Male a long line of 100 foundations. The first one you plant gets ID ■■■. Each piece that adds to it is part of ■■■ structure. Remove a couple pieces from the middle, leaving 2 lines of 40+ foundations each and both still maintain that same ■■■ ID number. If your storm requires 90 pieces for storm beasts to spawn on a structure, they will still spawn for you. Hopefully I relayed what I read correctly.
So if you make a main base, then want a smaller satellite building that is closer to the tower and wish it to be safe from attack, do not ever have it connect to the main base.
I hope this helps in storm base planning for all the private servers and solo games that enable siege beasts. If you aren’t enabling them, you will miss out on a really fun part of the game 
