The vibration is from the four cycling at low idle and just off of it. A total 2 cycle run would obviously be smoother. I can get it to run at an idle almost fully 2 cycle but then it is too lean to control. I am wondering if a carb designed for larger engines would flow fuel better and help out. If it isn't to big in the venturi for the engine cc size. I have a couple laying around I am going to check out.
maybe the 4 cycling idle wouldn't shake the plane to bad. It is presently on a test stand. And yes it is still the 42 I am working on.