Magento Shipping Extension -- 2

After several magnto developers attempting to fix an issue with our current shipping module we now have to look to have another shipping extension to replace current extension. We need it to allow us to create multiple shipping classes based on product size and then we need to be able to set multiple rates per country for each shipping class. At checkout we want customer to only be presented with shipping options for the item with the largest shipping fee in basket. We have a module set up with all rates for all classes and countries.