Is it possible to add new HeightSpec for Calendar as "BusinessHoursParent100Pct". It should show only business hours (not the same as current HeightSpec=BusinessHours which shows 24h) and must be 100% height of relative parent.
In the 6.5 release (http://www.daypilot.org/daypilot-pro-6-5.html), it will be possible to specify the displayed hours range independently of the business hours and HeightSpec using DayBeginsHour and DayEndsHour.
You will be able to limit the displayed hours using DayBeginsHour and DayEndsHour and still use HeightSpec="Parent100Pct".
The implementation is already available in the sandbox: