I don't see that as a slip pot. What are each pot's measurements?
I also don't understand taking a bonsai from a bonsai pot...for terracotta. But that clearly is a personal preference.
Adair always stressed not to mess with these roots except during their heavy growing period. That window has closed for me. Mind you I'm a northerner. I've got fall blush hitting my trees. But that's a pretty nice tree... to risk in my opinion. When waiting is wiser. A dead tree in a new pot is never an advantage.