Balanced number of sections in paper? Longer monographs should have an odd number of chapters [the
  Internet,1700-xxxx].


Does this rule also apply for papers? I've got a paper with four chapters and I'm wondering if I should make it five. I could split up the outlook &amp; conclusion part, but that would result in two really short sections.

What does the style police suggest?
I don't think that any style guide or policy (besides maybe some journal about aesthetics in writing) will force you to an odd or even number of sections or chapters. A scientific text should get the number of chapters it needs and not a number that fits aesthetic principles–basically you write it to tell the scientific community about your findings and not to please them.

If you manage to write a scientific paper in Haiku form, this will be nice but it may also make some referee think you don't take your research serious enough. More or less the same holds for odd or even chapters. If you force the text to fit a certain number of chapters by dividing a chapter into two pieces, the reviewers might also consider that bad style.