[Zope] zope.conf question

[David Pratt]

Hi. Is there a way to create an INSTANCE_HOME variable in zope.conf more 
dynamically than hardcoding the path. I want an app to be platform 
portable so this will be different?

Alternatively, I have been considering overriding zope.conf settings for 
use in zope.app.twisted.main and an interested in any suggestion for 
best approach to this.

In z3 services are started with:
service = setup(load_options(args))
args are a list ['-C', '/path/to/my/instance/etc/zope.conf']

In load_options, the default zope.conf.in is looked for else it gives it 
a value of None then options are utilized with options.realize(args)

Regards,
David