Full calendar - defaultEventMinutes

Full calendar - defaultEventMinutes

I am using FullCalendar from http://arshaw.com/ and I need to set the
defaultEventMinutes for the event directly, is it possible?
I have 3 external draggable events and all events should have other
duration (first should take 10 minutes. second 20 minutes and third 40
minutes), so when I set the full calendar property defaultEventMinutes to
20 minutes, it is not good because when I am dragging the event to the
calendar it shows me only these 20 minutes in different color to drop.
I cannot set the end date of the event because even the start date of the
event is not known.