A shape like an S is going to be highly anisotropic with regards to flexing and rigidity. Yes, more walls won’t really help if they are not in the direction to resist the force in question.
Like someone else mentioned, an I beam is basically as strong as a beam with the interior filled in, because that’s where the stress goes.
Off topic, but isn’t disney going to sue you to hell and back for profiting off their venm diagram mouse logo thing?