That is a good graft.
I've heard several, somewhat conflicting, stories about grafted Zuisho. The story I've heard from Boon is that around 60 .years old, the grafted Zuishos are all failing because the graft union fails because of the different gtowth rate of JBP and the Zuisho. He tells me he hears this from Daisaku and Akio. So, he tells me the way to go is to ground layer the zuisho. Let it have two root systems for a couple years, then remove the JBP. (Same for Kokonoe).
Juan told me he heard it was the ones on their own roots that were failing. He said they grow so rapidly when they're young that they're just not long lived. But, he said the grafts, on the more robust JBP stock are doing fine!
Two completely different stories!
I'm leaning towards Boon's version since he atttibutes it to Daisaku and Akio. Daisaku in particular is a JWP expert.
I don't know if there's anything you have to do to make a ground layer happen, or whether you have to strip out a section of bark.
Anyway, good luck with whichever way you choose to go!