Save your 220 Shanghai leaders and tails, carefully, in case someone starts to release 64mm film in bulk rolls.
If you've a bunch of these papers you do no want to use yourself, drop me a PM.
I have several 220 Hasselblad backs, later models, I believe, and use them with 120 all the time.
Any differences in size of the backs are nil, so far as I can see, so just loading the 120 format films is as simple of no fully rolling up the leader to the triangle mark on the lower bracket
That's the real value to these backs, when found in good kip and at bargain prices compared to the A12, lately.
I like to keep an empty 220 back on the CM, so I can practice handling and composing on the Camera, as well as keeping it on when I work each of the lenses shutters for top maintenance.
IMO