Stock only exists for models.
If it's not working with models and options, consider revising how you organise products all the way from the categories down subcategories, products, models and then options. It doesn't work for everything, but you might have more success with a different structure.
If it's not working with models and options, consider revising how you organise products all the way from the categories down subcategories, products, models and then options. It doesn't work for everything, but you might have more success with a different structure.