I was intending to watch that very video. Thanks for sharing. My only concern with using larger log pieces is the nitrogen it requires to break down the
carbon. Larger tree branches contain a higher carbon to nitrogen ratio, and could pull Nitrogen from the surrounding soil. Smaller branches have lower Carbon to Nitrogen ratio so won't require as much Nitrogen to break down. Clearly it hasn't hurt James plants any.
For me, and I'll be working on this same
project soon, if I use larger pieces I think I'll make sure to add Nitrogen rich souces too. Mostly
urine, which
should counteract any Nitrogen loss. I am planning to pack last fall's rotting apples, food scraps, leaves, and garden prunings around any wood or branches before I add soil/compost on top to plant into. I intend to use the leaves and drier materials to create space-oxygen space, so the apples and food scraps don't get anaerobic. That's the plan anyhow. Raspberry & Bosenberry will be planted on top.
Hope it works.