jm V¶´üO@¾¯Þs$VunGü1?aí<ÆL¤I'm reading the jasonc. The double spend depends on some miners filtering out low fee transactions. Off hand I don't see a need to filter out low fee transactions.
https://whatsonchain.com/tx/c1b3994a973d35b7c0093b5b3cebcdc060643a3882723bf2c45c3e06cea0cb8f