If you use SizerLight it will adjust the height and font of the ComboBox without any code (don't have to set DrawMode).
I don't think resizing the height/font of a ComboBox was intended for C1Sizer. This control is used more often for forms that keep buttons and text boxes uniform.
But the documentation does say that the height of a ComboBox should expand if DrawMode = OwnerDraw* but I cannot get it to work either. It's either a bug or not intended to function.
If you'd like, please submit this as a bug here
http://www.componentone.com/Support/SubmitIncident.aspx
and post your incident ID in this thread.
Thank you,
Greg L