ZCS 7.1.1 won't allow double booking

[infosyst]

Since upgrading to 7.1.1 we are unable to double book locations. This worked on ZCS 6.x prior to the upgrade by setting

zimbraCalendarResourceDoubleBookingAllowed TRUE

for each COS that we wanted to allow to double book. I have verified that the setting is still in place, but when users save an appointment they simply receive a message stating that the location was busy and could not be scheduled.

Any ideas as to how I can allow an override for this? I just want to allow certain users to double book locations/resources.