Integrated headtubes?

In the headset dialog box, you can select different appearances for your headset. There are a few options you can choose that will give you the shape of an integrated headset. Next, enter the lower stack height for your integrated headset. Integrated headsets will generally have a smaller value for lower stack height than headsets with external bearings.

You may also wish to go to the tubing dialog box and select a variable radius head tube.