Ok, this gives us a better comparison. I will do that tomorrow (now at home, it is 7pm here).
Today, I used a 35mm negative with the 60mm and the IIc remained in focus to postcard size, plus or minus. I didn't have time to measure but the longer side was plus minus 15cm (5,9in.).
So, you're right there's something not okay. Sofar, I don't think my 60mm is further extended than yours.
I always forget the precise action of the small wheel doing its part on the cam . I will also look at that tomorrow.
Have you looked critically at your Bowden cable, the part at the rear in particular? When the black protection has come loose from the shiny aluminium, there's a problem.