Syndrome, that is correct. The diameter should be nearly identical to the Yoke unis. There is going to be a little bit bigger diameter just at the point where the clips are, but this is a total of maybe 1mm more overall and usually at a point where they are not in the way of hitting, at least nothing was mentioned to me by the person running them in the Yokomo. I have personally not measured the Yokomo units, but I know they work.
For what it's worth, the XRAY, RSD and Yokomo Universals have interchangeable parts, they all have the same measurements. When we designed ours, I kid you not, the dimensions were practically identical to the XRAY units and we DID NOT EVER measure the XRAY ones. It was pretty weird. Come to find out, the Yokomo ones are the same way.