The Metro theme bears a different control template for RadScheduleView than other themes. To reduce the size of slots in MonthView you should edit the MonthViewBottomLevelWeekGroupStyle and set margin and padding to 0. Also remove the MinHeight.
Next, set a fixed size to the RadScheduleView control.
If your scenario allows it, you can hide the week group headers or remove the layout transform so that they appear horizontal. Both will result in reduced MonthView height. A sample is attached.
Hope it helps.
the Telerik team
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