Every 620 camera I ever had was a little different... The ansco ready flash I just sold on
ebay as a pinhole would take a 120 supply side roll and I could modify a 120 spool on the take up by cementing a bit of roof flashing with a smaller hole for the knob to fit inside. It is by far the easiest.
I have a duaflex I'm going ot shoot for the pinhole thing. I can't even get it to take a 120 in the supply side, even if I trim it down. Im going to reroll one roll just for the pinhole shoot. And Never buy another duafex. I can get the roll in, but it is so tight that it hurts my hands to advance it.
The
ebay aution is still going if you look closely you can see the spool on the table has a second top on it
The added top thing I did to convert a 116 to 120 as well. If the camera will take it, thats the easiest way to go. Some will some won't. The 116's were kodak by the way so its just hard to tell what will and what won't let you use different techniques.
The folding brownie I distroyed was very early and used 120. It was a wooden frame (ie cigar box) and had warped. It leaked at the back so I changed it to sheetfilm.
When the guys made six twenty they either just changed the advance knob design, or they made the compartments just too darn tight. There was no reason for either except to limit the brands of film you could use. At least that's what I've always heard.
They show up on ebay from time to time but are so darned expensive I stopped looking for them. I agree if you cant cut down a spool but the film and reuse the spool. The empty 620 spool is probably more expensive than the film.