For the UltraDayView, how do I stop the start/end time from showing up?
The following KB article demonstrates how to do the opposite, that is, always show the start/end times, but the approach is the same. Note however, that it was written before Office2007 support was added, so if you are using that ViewStyle, it requires some modifications. If you need direction for that post here and we will try to help.
I can't find any attributes called DisplayStyle, TextDisplayStyle, or AppointmentTextDisplayStyle to alter.\
Where I can assign this?
There is a DisplayStyle property (of type AppointmentDisplayStyle) exposed by the class that implements IUIElementCreationFilter. You can either store a reference to that class, or cast the contents of the control's CreationFilter proeprty to that type and access it that way.