We have done it the opposite way riding three 250 Honda NX,mid NOV 2
No problem with the depth,but the strait line is not always the good one. If no one is around,check for immerged big boulders.
Most of the time,there were ladies washing or kids playing.
After 5 or 6 river crossings,you'll be up in the mountain,pristine jungle,with
2 passes(elevation 1100m and 1300m).Only 2 kamu villages,bring some food and water.
Don't forget to close back the fences barring the trail
Ten Kms before Hongsa,you ride down to the last Village,Ban Napoung, where is the last river crossing. 2 more kms and you turn right at the T on the trail coming from Xayaburi.
Total kms to Xienmeme(across Luang Phrabang) 138.
Enjoy the ride as much as we did.
PS, sorry i still don't know how to send pictures on a post.May be later this month as a good "expert" friend is coming home.But at 70,you're slow learning!