Last year my stock were never split, just moved them over into a different loft with slope back perches (no boxes). Put them back over into their own loft the same time as I paired up my racers (which were split) and all stock laid out the same time as the racers. What did happen was one pair of stock took over the floor and yes the hen laid out but this pair stopped all the others from trying to pair up in the corners, chasing them back up to the perch.