Alan,
> Perhaps there is a related Dia practice that I have
> overlooked. If not, this may be a useful example to
> emulate.
Are you aware that you can put custom shapes and sheets
under
$HOME/.dia
(or %HOME%\.dia on Windows)
These custom sheets will be available in all the different dia versions that
you've installed - Make sure to find the .dia folder or set the HOME
environment variable for this purpose.
Steffen