See the older History Channel, 2-part series from July 2016, for more on the Igram find. Dwayne says a little too much in the interview at minute 62 of episode 1. The same information is given in Colbert's book, The Last Master Outlaw... [page 188] ... "see them two little sticks right there" after young Brian cleared his first spot for the fire.
In addition, see the Ingram's reaction at minute 68 in the same episode 1, where Dwayne and Brian watch the Ron Carlson interview pegging the "hippie couple". Similar explanation in the book [pp 166-68].
This Dropzone forum was down during that period and I never saw any discussion on any of these points on the other forums. Seems like two big keys regarding the 'money plant'.