I did an Airworthiness Certification on a Ultrasport U/L helicopter.
The builder said he had to redesign a good deal of the machine and wasn't at
all impressed with their engineering.
He has been flying it for several years and also tired of having to rebuild
the Hirth every year after an unexpected autorotation. He re-engined it and is
now quite happy with the aircraft.
I was surprised at how many major things he had to change on the airframe.
I am very active in sport rotorcraft and this is the only non-factory
Ultrasport that I have heard of that is flying.
In all fairness his could have been a very early model and as such still had
"bugs" to be worked out.
Good luck, Tom