I'm assuming, in my reply here, that you are concerned about possible discomfort from the carbon fiber tubing rubbing against your back.
The two vertical pieces of carbon fiber tubing are 12" apart and inside tight fitting sleeves (1" wide nylon twill webbing) on the surface of the pack. They don't stick out much. My shoulder blades are less than 12" apart and my back curves both vertically and horzontally. So the pack bag is usually what touches my back. The pack and my back only come together for a few inches around the shouder blade area.
I've made one of these packs for my 5' 2" wife and my 6' 5" friend so far. They have flatter backs. My wife has used her pack for several years now and says she has quite a bit of pack bag to back contact but does not feel the carbon fiber tubing. I don't have much feedback from my tall friend yet. I only recently completed his backpack. He was concerned about the carbon fiber stays bothering him before I made tha pack but says, so far, no problem.
The position of the pack bag on the frame and the position of the frame on the waist belt and the curvature of the carbon fiber tubing and all the cinch straps are adjustable. So one should be able to remedy any discomfort if it occurs. I change the postion and fit of things as I hike to adjust to temperature and terrain changes.