Thanks, photon46. I've seen that diagram and I told a+ in my email that the max diameter that the xhadow can accommodate is 7mm (according to that diagram). Yet, no definitive answer from them. I don't have calipers, but when I eyeball it on a straight ruler I get ~7mm for the cable's diameter. Too close to call? I know 9mm will work since that's the diameter of the wbt's, according to their data sheet.
But Ct0517 has given me another idea that I might pursue instead: a continuous run of tonearm cable from headshell to phonostage, running external to arm. Has anyone tried this for a pivot arm?
I would still like to have a definitive answer to my original question.