What I am trying to do is to convert this airplane into pleasant to fly machine. Nobody could explain to me where elevator vibration was coming from. I was simply assuming that that was result of horizontal tail working in all kinds of separation from fuselage. So, I was trying to clean up airflow.Not sure if you are trying for very low drag,
What we know today is that 120 mm tail tube is simply too small to handle moment from 100 HP engine and CG spread from 21-36.6% MAC. Tail is flexing and jumping in flight and driving you crazy.