For me, the key to the money find is, was the money placed at Tena Bar intentionally, or did it arrive there unintentionally? If it arrived there unintentionally (dredge, currents, or was there since the skyjacking), then I assume it either detached from the Cooper suspect and both hit the earth's surface not to far from each other, or they hit the earth's surface together. Either way, it would seem the money was in either one or two locations since the skyjacking.
On the other hand, if the money arrived there intentionally, the prime suspects for planting the money are the Ingrams, Kenny or Duane.
The more information and opinions I read on the subject, the more I'm convinced that the dredge can't be ruled out.