May I suggest removing more than just what is painted blue?
Wow! I don't think this will be my option. New tail boom will slide somehow over old leftover 120 mm tube to make tight fit. I'm not sure how it's gonna look like, but assuming there will be no play at all. There shouldn't be any play or possibility for any adjustments.Make the entire boom adjustable.
-I am alive,Just to mention it: That counter-rotating prop thingamajig that henryk frequently brings up might address some of the issues being experienced.
Henryk, where are you?