The project has hit a rather large bump in the road: due to “special circumstances in Xinjiang” my contact in China is unable to obtain the invitation letter I need to get my visa. I'm told that if the China Tourist Service in Xinjiang is unable to obtain the letter, it is unlikely that any other agent will be able to obtain the letter, and therefore crossing the border into Xinjiang "may prove impossible at this point in time". This, I am told, "would have been a high level decision, which also means that it is unlikely that there will be a later change of heart."
Definitely not the best news of the day.
The maps are back out. China is now a big obstacle between Kazakhstan and Vietnam. Suggestions welcome!