Now if everyone just stopped goofing off in shop and math class , or on the computer they could of built the Hiller XH -44 in their dads' garage at the age of 19, just like Stanley Hiller. ....or so the story goes.
The "original" Sikorsky ABC concept got its start in Stanley's garage, with a two blade rigid counterrotating head. There are clips on YouTube. Besides the maple seed, It actually probably gots its start with the turn of the century "Wright brothers" types with their steel tube and fabric, hopping contraptions. Scratching their heads , not knowing that without the teetering hinge the rotor will roll to equality vs flapping to equality. Stanley wasn't preoccupied with the two legged birds so he had this all figured out and made a counter rotating head to cancel things out. I can't seem to find the tale of vibration in the story but would guess from the UH12 rotor quickly superseding the xh -44 's enroute to mass production that it lurked not far beyond translation.
Apart from the vibration caused by the inevitable poor bedfellows of coning and flapping without an underslung hingeline ( or multi blade head that is called "rigid" but accommodates some lead lag) I would think the stability and gust response on a single rotor design would make the Boelkow 105 seem a docile beast in comparison. Lockheed anticipated this on a model prototype in the 50's building a rigid two blade that was stabilized by linking it to a gyroscope ring atop the rotorhead. Needless to say they quickly abandoned it due to vibration in favor of 3 and 4 blade heads in the lead up to the Cheyenne project.
I say follow Stanley's lead and build a model RC helicopter refit to a rigid two blade head slowed down to 300 to 500 rotor rpm. I'd advise motorcycle gear and hockey equipment. Happy Tinkering