Well... what the what? I thought i had the images attached to the thread and now they're nowhere to be found. I had a hard drive crash, so i'm not even entirely sure i still have the pictures. I'll have to look around and see if they're backed up somewhere in the mess of backup shenanigans i have. I'm actually a little surprised to see this pop back up.
I'm not sure if the backing paper or film was thinner on 620, but i didn't tend to have any real issues with binding of the film / paper, only the spools. I thought the spool could be smaller because they were made of metal and had a thinner core, not because of any thickness difference, but i may well be wrong. That being said the winding on mine was never what i'd call "buttery smooth", largely because of my seat-of-the-pants engineering.