I think you are underestimating your onions! They are perennial, you know, and in my experience they 'bunch' at least once a year, and sometimes twice. Right now mine are in the middle of dividing, and it's not unusual for one plant to morph into 6.

You are late getting them out, but I bet they will still bunch in the fall. Then, you dig up the clump (which has now grown to 12 inches across), replant a few divisions, and eat the rest. Next summer, the ones you replanted in fall will bunch.

I do think it's a good idea to move them to a new spot each time you replant to avoid problems with root maggots.

Thanks planatus,

Never raised these before, and am looking forward to a weed and eat permanent planting, so am curious about the ideal depth and first season spacing. Should I plant them in mini-clumps, ie 3-5 stems per planting hole? Maybe I will just experiment and try some simgle 2" apart and another row of clumps. Have not met anyone in my area who has these.
Have always used wood ashes, and so far have not seen root maggots.