ASPDNSF does not support commercial rates out of the box.

When I set the RTShipping.USPS.Services appconfig to "Priority Commercial",
here is the result:

<CommercialRate>xx.xx</CommercialRate>
<Rate>xx.xx</Rate>

Where in the source does ASPDNSF look for the Rate XML value? I would like to change this to grab the CommercialRate tag