How would you slice this tephrocactus and which rootstock would you use?

I was thinking about cutting this into three or four pieces and using opuntia as rootstock. Does that sound like a good idea, or would you do something else? I’m new to grafting and would welcome any tips or advice.

Opuntia seems like a good choice because it’s genetically close to tephrocactus, grows well in my climate, and I have a nearly unlimited supply. But I could also use PC, oa, pereskiopsis, or dragonfruit.