Quote Originally Posted by numinix View Post
USPS and UPS are not supported shipping methods. Only the ones listed in the dropdown.

You said you set the method as "per weight unit", was this module installed and enabled in your admin?

You can see the calculation if "per weight unit" is selected:

PHP Code:
$rate = (MODULE_SHIPPING_PERWEIGHTUNIT_COST * $products_weight) + MODULE_SHIPPING_PERWEIGHTUNIT_HANDLING; 
Obviously if the module is not installed, those constants would have a value of 0 and (0 * any number) + 0 = 0. I can add checks to make sure a selected module is installed, but this will simply add more processing time. It should be obvious that in order to use a module, it has to be installed.

Same thing will happen if the products_weight is 0 and there is no handling fee...
Turns out you were very right and I didn't have the perweightunit module enabled. I don't remember seeing to turn on in the documentation.html which I think would help.