I agree with you on micing the room corners. It does give a baseline for room mode and depending on results it can show a room anomaly that can be helped by an acoustical treatment. The placement of the speakers is determined in large by where the customer wants them. There is always a little wiggle room and when you evaluate what you hear and what measurements look like you can make a placement change. For the most part the speakers already have a designated place in the home. been good chatting, take care.