Line width

[Simon Siemens <simon siemens arcor de>]

Hi Michael,

the base units are indeed centimeters. I can now adjust it and also set
an appropriate line width for the frame of the class. Thanks for that
hint.

Now I got stuck with the line width of the arrow, though. A class
derivation arrow seems to have a fixed width, which is quite large. Is
there a possibility to change it? The same applies, for example, to the
branching symbol.

Thanks, Simon