Dan, I have changed the BusinessBeginsHour and BusinessEndsHour to my required ours (9-5) and but I am still seeing the hours before 9 and after 5. All that seems to do is change the colour of the background between those hours.
This may be a good idea to add to the product.
Regards
Andrew
Please see here:
http://www.daypilot.org/scheduler-hiding-non-business-hours.html