For every shipping service you add, there is a possibility to attach shipping labels. This makes it possible for you to connect a shipping service to a group of offers.
From the shipping services page, press "Add a shipping service"
Choose "Provider", "Service type" and create a label for it (e.g "Oversized")
In your product feed, you can then label offers with shipping labels according to
shipping_label(read more about
This way you can control which shipping services are available for which offers.