FedEx Shipping Method

When One Rate is selected it only uses that rate instead of choosing the cheapest rate from both regular express services and one rate. The Express weight-based services and the One Rate services both use the same boxes. They are dual-use boxes that work for either service. This is where you would check the rates for both services and return the cheapest result.
Another key point is that we do not want to confuse the customer by creating separate shipping methods for each of these because you would be offering different rates for the same level/speed of service from the same carrier.