Well, with the off center screw to lock the carburator I would say OS based, for sure with the story about the best plugs from Japan. Ofcourse all is produced in own house as many OEM brands dare to advertise with but I know Hudy can do this.

I do know 6 years building from scratch is a normal tme to get a competive engine but on the other hand if you can not get it right and do want to have an own engine line the only option left is to talk with current engine manufacturers.....