Death Star in 4 parts - Remix

I was having trouble getting a clean seam so I split this into 4 parts. Top, middle, bottom and a key. The holes are 20x20 and the key is 19.5x19.5 so it should fit snugly. I had to trim the interior edge of the holes. I also made it round. The original model was off by just a fraction of a mm and I didn't even notice until I got it into Tinkercad.

This is the Tinkercad link.
https://www.tinkercad.com/things/1coqW7BBGsW-death-star-4-part

I only supported the holes in the top and bottom.