Due to the Corona problem, I can't get any thin-walled aluminum tube at the moment. Therefore, I have pimped my old and very much used PVC resonance tubes with a new type of flap.
The new flaps are printed from flexible plastic with a hole "too small" by about 0.1 to 0.2 mm. Therefore, they adhere very well to the shaft after sliding on, but can be aligned and positioned as desired.
I also managed to make this solution foldable. Due to the magnetic coupling, the shafts reconnect by themselves after splitting.
Another advantage is that the shafts (bearing blocks), which are also magnetically fixed, simultaneously prevent the resonance tubes from falling out during transport as a "folded pan flute". Nevertheless, you can simply pull off the shafts and put the tubes into each other individually (tube-in-tube concept).
The flexible plastic of the flaps makes the whole thing extremely robust and almost unbreakable.