Transportation Routing on outbound (sales order) collect shipmentsHi

We are using Transportation module for inbound and outbound shipments. Most of our outbound shipments are collect and the customer picks the carrier. We setup the preferred carrier on the customer master record and it comes into the order header automatically. The CSR checks and may change it. In this case should we setup our freight handling code to bypass routing and rating? By default collect shipments are auto-routed UNLESS carrier and MOT are overridden says the docs.We are not setting up a route for every carrier, as the carriers are endless - every mom & pop carrier known to