Larry, because of the way yours is set up and because it is not like the COOT machines that I am familiar with, I asked if yours was a prototype. Honestly I would suspect that yours might just be such a thing.
I have a tractor that works like your COOT. Articulated in the middle with 4 wheel drive and the articulation is what facilitates the machines ability to turn. It has limited oscillation of, I think, 8 degrees from the rear right to the front left & visa versa. The production COOTs that I am familiar with have at least 45-degrees of oscillation between the front/rear. Your unit looks to have minimal oscillation but clearly has the ability to turn a very tight circle.
Any idea how much vertical oscillation you have from front to back on the opposing wheels? It does not look like you have much oscillation.