I've been kicking around a pet theory on the relationship between instinctual variant and enneagram type for a while now, and am seeking some feedback on it.
Basically, the idea is this: start with the assumption that everyone's enneagram type is dual winged. We might have a stronger preference for one wing or the other, but to some degree exhibit traits of either. I believe that how we exhibit our instinctual variant is tied to this idea. The arena in which we express our dominant variant is dictated by our core enneagram type, the auxiliary type by the stronger wing, and the third instinct in our stack by the less expressed wing.
For example, in my own case, I am an 8w9 sx/sp/so. 8-sx would suggest that the primary fixation of my sx energies is not so much relationship, but power. It makes sense as I have a very instinctual understanding of power that resonates with the sx-dominants attunement to energetic relationships. 9-sp would bring the comfort-seeking aspect of sp into focus, but also suggests an element of self-forgetting--a minimalist approach to one's needs.
I get a bit murky when I get to the third instinct in the stacking. My belief is that 7-so would suggest something energetically akin to dominant extroverted intuition. The diffuse So energy being cast in the mental plane, heightening the need for intellectual variety at the expense of intellectual depth, and perhaps emphasizing interest in subjects pertaining to culture or other social subjects. I think that the tertiary instinct is not so much suppressed as it is unconscious. I agree there is a sort of ambivalence regarding the expression of the tertiary instinct, but in a way I think that it's the least complexed of all the instincts. It doesn't carry the same baggage nor hold the same connotations as the first two. We relate to the energy in some combination of the ways that we approach the relief and inferior functions in MBTI.
Anyways. I've played with this concept for a while now, and am now wanting to see how it fares among minds more knowledgeable than my own. If anyone's interested, I'd love to be able to try the model out on them to see if it holds up.