How do I change from min 2 nights on weekends?

A tricky one here. In my calendar setttings I have my availability settings set to a minimum of two nights for stays involving a Friday or Saturday night. No problem and works well.

However, in a few weeks time, I want to change the Saturday night for just one night. (Have bookings either side). Under the availability settings, I put in a special “Reservation Preference” - Specifically: “During 26 Nov 2016 – 27 Nov 2016, guests stay for minimum 1 night.”

Trouble is it doesn’t make that night available for the one night. I though the reservation preference would over ride the minimum two night requirement for weekends.

Any ideas or solutions how to get around this would be much appreciated.