When the opposing pendulums system was developed, there was no literature or evidence that such a system had been developed ever before. Graeme wrote a paper on the successes of the system and submitted it to the Journal of Arboriculture, however it was later published in ArborAge magazine in the 2000 October/November edition (Vol. 5, No. 3). You can download the abridged ArborAge Opposing Pendulums Article.
We regularly present this rigging system in advanced rigging seminars as a potential solution to difficult tree removals. If you are interested in having this system presented at your next arboriculture conference, rigging conference or company training day, check out our seminars page.