I have no pain with either of the Underworks binders (the tri-top or the full tank). My recommendation would be based on how active you are during the day and what parts of your back you have the most pain in. I have a lot of lower back pain and several spans of otherwise dead sensation zones along my thoracic spine that will get tingly if I'm doing too much. That said, both of these issues existed way before I started binding and I don't feel that they've been exacerbated by wearing a binder.
If you're going to be doing a lot of moving around, I'd say go with the tri-top. Even with my chest range spinal pain, this style hasn't been an issue. But I could see it being a problem if you feel pain at the bottom edges of the binder, because it rolls up about an inch and puts a little more stress on that area.
If you're more sedentary during the day, I'd say use the full tank style. My only issue with it is that it constantly rolls up at the bottom and it bothers me to the point that I need to go to the bathroom and adjust/tuck in my binder and undershirt at least once an hour when I'm moving around a lot. I don't have any additional back pain with it.
