Hello,
You could use the C# Partial class to prevent to have several classes and to decrease the number of files to manage.
For example, instead of creating a class "TimeCard" in the "Timecard.cs" file and a class "TimecardImpl" in the "TimecardImpl.cs" file, you could create only one partial class "Timecard" with a generated "Timecard.cs" file in the target folder and a user "Timecard.cs" file in the src folder.
So, you let designer to choose its own base class, to choose all its classes.
Thanks.