With Volusion, you can assign a special shipping method to orders with an extreme weight or circumstances. While there currently isn't a function to assign shipping methods on a product-by-product basis, you can use the existing shipping method controls to create a custom workaround.
You should not use this method if your store has any active live shipping rates. If you have any live shipping rates active and an extreme-weight product is added to the cart, you and your customers will experience extreme delays on your store's shoppingcart.asp and/or one-page-checkout.asp pages.
Make sure that no feasible combination of other products could meet or exceed this weight.
From the Admin Area, go to Settings > Shipping.
Click Add Rate next to the Flat Rates heading to create a custom shipping method.
Enter a name for the method and mark it as Active.
Enter the shipping cost for products using this method in the Base rate field. Make sure the Cost Per Lb field is blank.
In the shipping method's Qualifying Orders section, configure the Minimum weight to an extreme value, such as "6000".
The configured shipping method will now be applicable to products that have with a weight of "6000" or higher. To set products with a weight so that orders containing them will only use this method:
Go to Inventory > Products.
Click the Product Code of the product for which you want to use this method.
Set the Weight of the product to "6000" or whatever you used in step 4.
Don’t let the heft of some products weigh you down. Volusion has a solution for you to get those extreme cases handled without impacting your other orders.