am I able to use the 72 hour Transit Visa in Beijing

Dan, I think you can travel under the 72-hour transit permit. I read a post from a guy a few days ago stating that he used the 72h free transit in Beijing even though his layover time was 74 hours. He said he had to explain to the staff at Heathrow to check the timatic website and took some printouts with him about the 72 hours starting at midnight and they gave him a boarding pass. At Beijing airport it is really easy they don't count the hours as long as you leave within 3 days you will be fine so they just stamp your passport after checking your onward flight details and ask you if you're there for 3 days just say yes and that's it...