Also, be careful that if you are going to use PWM that you don't exceed the base fare with the amount reducing the tickets. There was an issue that if you pay for all of the base fare, but still charge a card for the remaining taxes and fees, it earns nothing. There was a separate thread and I'm not sure how it was resolved (if there was a resolution):

For example:
JFK-LHR-JFK Base fare: 599. Taxes: 200. Total if purchased outright: 799.
If I did PWM and I wanted to reduce the ticket by $600, those miles would eat all of the base fare first. In effect, you'd be paying $199, but only for taxes and fees. You would earn no MQDs for the taxes/fees portion and you wouldn't (at least in the past) MQMs either because you had no dollar amount left in the base fare.

Compare:
JFK-LHR-JFK. Base fare: 601. Taxes: 200. Total to pay outright: 801.
If you did the $600 PWM discount in this example, you'd still be left with 1 dollar in the base fare. It would earn 1$ x your MQD multiplier and full MQMS.

If this issue has been resolved, please let me know.