@Hammer I just bought a used cinelli spinaci extension (for 20€) to try to fit the airstryke design profile extender to the end of a handlesaddle.
I didn’t do the measurements, but if I understand correctly the handlesaddle has a section of 24.5mm and fits perfectly with the cinelli spinaci.
That means that on the other side, the section is 22.5mm… did you cut a 22.2mm tube? I guess to fit my extensions, I’m going to need 31.8 - 22.2 shim.
EDIT : I measured the handlesaddle, it has a section of 22.2 mm… and yes 1" = 25.4mm