Hi Josiah,
Now i am replacing all my small objects like trees, lights ... and doing scripts for them. I have a big real city. My city has many small objects. Trees 3000, lights 2500, advertisements 1000, so on. I placed all these object on my ground, and FPS was really bad 0-1FPS. Now it is increasing, after changing my trees it goes 10FPS. I decided to change it all.
My algorithm is very simple, if you want i can share it to contributions.