I agree that fn_size should be disabled, as the style guide says "no hard limit is placed on function length."
https://google.github.io/styleguide/cppguide.html#Write_Short_Functions

But I think you can just add -readability/fn_size to _DEFAULT_FILTERS. No need to remove anything.
https://github.com/cpplint/cpplint/blob/34a534a786729408fc5d4ed91d28eeb0b6d1e6e1/cpplint.py#L414

@matyalatte you're right, that's a much better and simpler fix 👍