I'm working on a 116 Autographic Junior right now so that color shot was of interest to me. Which lens does it have? Besides the instructions given in the PDF for adapting 120 spools I have seen where someone has taken dowel and inserted it into the cutoff end of the spool then slotted the dowel.
I'd be interested in the anchor sizes you used. You must be using the straight anchors? Did you do anything for a pressure plate or did your camera have one? Mine only has two long runners at the extreme edges so I need to adapt one to the back.