SC Fly Tyer,
Please don't be put off by Mr. Carne. I'm sure he means well, both for you and for the art of tying the classic fly. Keep posting, etc.
Nevertheless, whether one agrees with using the wing setter contraption or not, there are some interesting things to be learned from it. For example:
1) It works by compressing the wing fibers at the tie in point, using only vertical motion. If the vise is set up right, then the force is only in the downward direction. This is an important lesson, and one of the eye-hand-coordination things to be learned. So for the tyer that uses the traditional winging approach, we learn when compressing the wing fibers, first by holding the wing in the left hand with the "vulcan death grip", compressing the fibers at the butts with the right -apply only vertical motion and force - absolutely NO horizontal motion. Then when applying the thread wraps, one needs to pull the thread in the downward direction only, again absolutely no horizontal motion. Some people use the hook shank as a pully and pull the thread up from the near side of the shank, again - vertical forces only.
2) It works by having the wire loop be a tight U-shape. Why? this maintains the vertical alignment of the stacked married wing fibers at the tie in point. So when tying the wings using the more traditional method, the left (wing gripping) hand must not torque nor rotate, and the wing must maintain the vertical position. For those with small fingers, like myself, this is accomplished by gripping using the thumb and middle finger, rather than thumb and index finger. The middle finger and thimb are more equally opposed, and hence prevent the torquing or rotation.
Thinking about it, or even using the wing setter, just to observe, may result in even more lessons, which, we would appreciate being posted for the rest of us. Oh, and I have never used one of these on any fly I have posted here.