Hello Gregr,
nobody would be able to use the efneo on a C1.
It’s exactly the same situation than that of ATS/Schlumpf drives - beltwheel with 80 teeth and freewheel with 30 teeth will lead implicitly to collision of belt and bottom tube - no way.
boxbike got meanwhile reply from MIng cycle - they tried to mount an ATS in the factory and stated: “…2 speed drive can not be used on the STRIDA C1…”
Kind regards,
Chris