At our conference we wanted to use frab to submit lightning talks (5min), talks (30 or 60 min) or workshops (2 or 4 hours). Having configured a timeslot duration of 5 Minutes results in submission with a wide range of durations. It would be great if it would be possible to configure fixed time slots instead of a time range for events, so that submitter can't choose from 00:05, 00:10, ..., 04:00 but just from a few fixed time slots like 00:05, 00:30, 00:60, 02:00, 04:00.