For the past week or so I've started to study Enneagram more in-depth, and a question has occurred to me: is there any link between the instinctual variants and the tri-type? For example, if one were a 2-9-7, so/sp/sx, would the 2 type and the Social instinct be linked? And would the person, when dealing with Self-Preservation matters, shift into 9 mode, etc.?

Something like this:
2-so
9-sp
7-sx

I'm just wondering if there's been any writing on this idea, or if it's even reasonable, or what. It's just a thought that occurred to me, which seems internally consistent, but may or may not be valid.