I would hate to be the guy that lifed the hub bearings on the BO-103!!
Even though the mass balance is there, effectively it is as if the cyclic was going around the box at Nr. The vibration must have been awful. The mass could have been set lower than hub to generate an equal and opposing hub moment to the lift, but this would only work for 1g. Any actual cyclic input would still lead to out of balance moments, hence a means of 1P vibrational energy getting into the structure.
I wasn't sure if that hub was teetering - it's hard to tell from the hiller bar. However, cyclic vibration is why hingeless hubs always have 3 or more blades...