is it possible for me to use carrier rates, and set weight-based conditions? Right now it defaults to our boxes for larger shipping. I see I can add custom shipping weights but, then I lose the carrier rate shipping discount through shopify. I hope this is a feature. I just don't want to charge a person $8 for shipping on a 12 oz item. I'd like it to default to our smaller boxes on smaller orders. Thank you in advanced.
You can achieve this case by using Multi Carrier Shipping Label App. This app allows you to customize live rates from top shipping carrier like FedEx, UPS,USPS and DHL. You can also set weight-based conditions. You can create your own custom boxes and app select boxes automatically based on the product weight.