Use this plugin and a weight class for perfect shipping prices

It is not necessary to define exact weights to all your products to have profit from this plugin. Even if your shipping costs are not weight-related but size-related.
You can define weight classes for yourself, f.e. 0-10kg=standard package, 10-1000=big or long package, 1000-100000=very big or long package, 9999999=not shippable.
Then you assign the shipping prices to these weight classes. All the products have a standard weight of 0, except the long or very big products, which you give the weight class of 10 or 1000. Not shippable products are assigned 999999 as weight.
For each region you can define your shipping prices now for each type of product.
And f.e. by giving a product a weight of 5kg now 1 piece of this product will have the standard package price, but 2 pieces will have the big package price. (That is the reason you have to define a big range for each package type, so a customer can order max. 100 pieces before he reaches the next weight class.)

Works perfect!