No, I've been maybe 15km up that road but it was YEARS ago -- at that time it was easier to get a sampan upriver from near Sekong, but the river was (according to locals I talked to) prone to flash floods and not all that safe. I didn't explore further.
I'm trying to track down the website of a Dutch couple I met who four-wheel-drove it -- will post it when I hear back.
I guess this guy is able to supply you with more information:
#3 3drazor has been a member since 13/10/2011. Posts: 16