I probably can't reliably increase the size of the structure past that. The game seems to only check chunks away. If I really wanted a super large structure, I might be able to get it to generate secondary structures 10 chunks from the first with well defined meeting points, but that won't work with how it generates now

V1.2 made major changes so the generation prefers pieces that turn it back to start more the farther it gets from the start.
If it still gets too close to the edge it will add the spawner tower and finish generation