If you can earn another $3K MQD, you could convert 75% to MQD and 25% to Miles (15.3K miles) and still qualify for DM. But if it will take you until year end to get an additional $3K, you might not want to wait that long to get your DM status. DM has higher multiplier for mileage earn than PM (11x vs. 9x). So you should also factor that in ($3K in airfare spend would net an extra 6K miles earned as a DM vs. PM).