MAX_PATCHES is caused when there are too many large surface areas, so much so that they cannot all be lit.
Usually when I run into the MAX_PATCHES error, what I do is scale up textures from the Surfaces panel. Do this for textures that don't matter / surfaces which you cannot see. For example, the sky, below the ground, outside of walls that they do not see, Etc. Set the size to 100x100, usually works wonders for me.
You can use the "Apply to face" button to scale up texture faces of brushes which players won't see.