Hey Paul, thanks for the upvote. I liked your recent garden updates so I followed you to see what else you will be coming up with.
Nothing wrong at all with your two compost bins, I'm using a similar one too as I have multiple types of bins. I also have one made of pallets for composting horse manure. Have you tried to put one of those two compost bins straight on the ground? Being open to the ground means the native worms can come in and out as they wish and spread the vermicompost along the way. That would work as a large scale of the Big Rotter.
Before I redid my backyard garden space, the bins were sitting right on the ground and, over the years, the edges had actually sunk into the ground 1-2". Now just the perimeter, or edges, of the bins are up on stone pavers but their interior space is still exposed directly to the ground underneath, so worms can move in an out as you suggest. The advantage to getting them up a couple inches is to allow the sun to hit the entire surface of the walls of the bins and to increase air circulation.
Ohhhh right! That’s very good indeed. I didn’t realise the bottom was still open. Very cool