A guy by the name of James Wilks has done it in a ducky. From the beta I gathered by talking with him was:
It is really long- 5+ days
No real white just a desert float, class I-II
Can only be run on big run off years, in peak periods
It is VERY illegal
Bitch of a shuttle
It is not my cup of tea but it might be what you are looking for, I hope this helps.