All the information from every book I have says you make your splits in the spring when there is a slight flow on or you are feeding one to one syrup.
Why can you not do Late summer expansions with new queens? I am thinking you could move the parent hive 100 yards and leave three frames of brood and bees and let the field force make up the rest with a new queen in the old location. Feed both colonies to make it through the winter. This would need to be done no later then the first week in August for the northern group. The honey flow is over and they do not have a lot to do? Give me some dialog and has anyone tried this?