Integration/disintegration is a type change. The idea of stress/relaxation points, however, does not imply change, because stress and relaxation are temporary moods.
Hm, I don't really agree with that. What's the point in becoming another type? What is the system describing then?
Integration is an expanding of the ego, IMO, which is adopting thinking & behaviors associated with other types which lessen the fixations. Disintegration is a narrowing of the ego where the fixation becomes more restrictive & extreme through the exacerbation of thinking/behaviors associated with other types.
In theory, you could transcend the ego, but I don't really think it's possible in reality. Even if you did, then you'd be NO type, but free of all the fixations & passions.
As for tritypes/fixes, I didn't believed in the theory at first. But studying the theory for a long time converted me over. The fact of the matter as it now stands is that the original enneagram doesn't explain enough. It's an observable fact that people evince qualities that don't follow the lines. Consider my own wife, whom I studied intently at first. I thought she was a 6w7, but she turned out to be a 9w8. 9 and 6 are related by a line, but her 6 traits aren't explained by stress or relaxation. She also shows some 4 traits, and this definitely doesn't follow the lines on the enneagram. She's a 964, or more accurately, 9w8>6w7>4w3.
Notice that her wing types (873) are all assertive types, while the main types (964) are relatively non-assertive, compliant or withdrawn. She is Supine-Choleric, and has a definite "split personality" going on that is inwardly conflicted. Part of her wants to run free with the party animals (8), while another part of her wants to stay home and take care of the cubs (9).
I think this is too much focus on behavior - which is exactly why you cannot explain everything with type.
Since types display some traits of their integration/disintegration points when average, that easily explains a 9 & 6 connection. Many types can have certain visible traits in common, but the reason for it varies, which is exactly why people sometimes have trouble typing.... Then if you bring Jungian cognitive functions into it, it would also explain why some 9s & 4s may look similar (both happen to be Fi-dom). What you might be seeing is Fi, not e4, and this counters some Si-ish aspects of e9 profiles.
Basically, your core type & its wings & their integration/disintegration points connect you to all other types anyway. That's more useful in helping you grasp how the fixations/passions of the other types tend to crop up in your own psychology, IMO.
Also, Borderline Personality Disorder is not correlated with any specific e-type.
Naranjo associated it with e4 (basically, something a very unhealthy 4 might develop), but I don't think individuals necessarily follow how their type tends to "break down".
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[MENTION=13377]pinkgraffiti[/MENTION]
I suscribe to the school of thought which sees instincts as manifesting through the lens of the core fixation. So an sp 4 is self-preserving through the fixation of being insignificant/defective & their passion for envy. It's more about an attitude and demeanor than literal focus. So the sp-dom 4 is the most contained 4 - "suffering in silence", tenacious in "enduring", masochistic or self-punishing for their sense of defectiveness. Other authors describe this 4 as "dauntless" which I tend to interpret as an indulgence to "self-soothe" their disappointments. I find these two concepts go hand-in-hand, as this indulgence is a way of being autonomous - you're not crying out to be fulfilled by a savior, but in denial of need & envy & using indulgence to fill your own voids. This is a masochistic cycle of shame & denial. There's a strong connection to e1 here.
In the more literal sense, the sp-dom 4 is focused on autonomy, soothing themselves with indulgence in luxury and beauty and novelty, other times becoming restrictive/ascetic in some ways, & keeping people at a distance to not threaten their emotional well-being. This is not about security or practicality, but certainly a "taking care of oneself", but in a more emotional way. But this "taking care of" can get distorted. I imagine very unhealthy sp 4s might be prone to stuff like eating disorders or self-mutilation. It becomes destructive.