I can simply put 35mm spool in place of 120mm one. Spring will hold it all right, and I can get it to wind on the receiver spool. Of course I can't know frame number and need to do it "by the feeling", but that's all right. My problem is film changing.
35mm film on 120mm spool always gets fat roll effect, because receiver spring cannot be used - it would scratch the film. And I can't simply open camera on the field because there is no lightproof layer.
Is there any way to use empty 35mm canister for receiver spool? Or any other way to protect film while it is taken out of the camera?