There is an option to setup a default on the product but we have 1000's of products and need a shipping rule that recognises length OR set length on a rework item that will change the courier if a long box is selected. Most couriers charge differently for items over 1.2m and we sell a lot of rolled up posters over 1.2m
I have edited my problem above as can now be more specific on the issue at hand. Setting default on product by product was not a solution when you have 1000's of items to change. Therefore my new resolution is clearer to allow for a simpler solution.
I would agree with this but can't you just a default courier switch or default courier on the box product?