I put two rolls of 120 into a single Patterson spiral all of the time, just load the first right into the centre, it is beyond the feed balls so does not move as you load the second film. When I load the second film I leave the last few inches wrapped around the spiral. There is no need for bits of sticky tape, I have never had a problem with the film overlapping. I do not alter development time. If you had loaded 220 film you would have used the volume of solution that covers the film at the standard development time and that is the same area of film as 2 x 120, so there is no problem.