@Aussierob: Redundancy (technical mechanics), resonance (harmonic oscillations, interferences, stimulations of vibrations), realiability (bolts, washers & nappy pins), please see my comments before. E.g.
http://www.pprune.org/9372108-post612.html
or what do you think about the 3-leg-theory and its redundancy? As well as a 4-rotorblade-system should have 4 suspension bars and a 5-rotorblade-system should have 5 suspension bars and those should be symmetrical? Ask some pilots which are also engineers.