windchill autonumber and "save as" in creo incompatible?

We are preparing the way to implement Windchill and Creo 2.0 in our business but I (possibly we) are struggling to understand the best way to proceed ref autonumbering.

We've been storing cad models and corresponding drawing files with the same filename (less extension obviously) so that doing a "Save as" in creo creates a new model and drawing pair (given appropriate config.pro settings).

With autonumber turned on in windchill doing a "save as" in windchill on a drawing and model pair creates a drawing and model with different numbers albeit they are dependant objects. The filenames we'd set to be the same as the numbers and so are also different.

If a "save as" is done in Creo 2 with the same model and drawing pair where the drawing and model have different autocreated "numbers" creo doesn't treat the files as a pair i.e. we've lost a chunk of the "save as" functionality within Creo 2.0 .

This is making it feel like autonumber in windchill and "Save as" in creo are incompatible if we're seeking to avoid manual renaming of filenames.

Hopefully I've made that clear enough ... are we doing something odd here? is there a secret setting to fix it?

thanks for reading

Mike