I have done it plenty of times in an RB back nad never had all the problems everyone says they had. I also repair RBs adn have never yet seen a single back damaged because it ran 120 in a 220 back. The rollers and preasure plate are spring loaded and will compensate for the thickness.

When you start the roll of 220 do you have any trouble winding? When you end a roll of 220 do you have any trouble winding? Both these ends are paper backed.