This is a tough one in that you can't really argue argue with Ferguson's results. But really many folks here (but by no means all) get our best results with bareshaft tuning as outlined here:
http://veraxservice.net/arch/tuning.htm
You see, paper tuning is only a snapshot of what the arrow is doing at one specific distant at one tiny instant of time. You can shoot a left tear at a certain distance, back up a few feet, shoot a bullet hole, then back up a few more feet and get right tear. Which indication do you believe?
But back to Ferguson, he is amazing, but keep this in mind, for his trick shooting he shoots one make and model of arrow at one specific length, with one specific point weight, out of one specific bow, while most of his high accuracy trick shots are set up to take place at one very specific, precise distance, exactly 12 yards. What he needs IS that snapshot in space and time. Nothing else matters.
For most of us here though, hunting, shooting 3D, and Field, although we may not shoot to Ferguson's crazy level of precision, we do need a significantly larger range of proper state of tune. Bare shaft tuning can provide that, for ANY distance you care to take it to. I myself take it out to 40 yards, and I know that if I have bare shafts grouping with fletched at that distance then I KNOW that I am achieving a decent state of tune without having to count on huge fletching to cover up a poor state of tune.
And honestly I only stop at 40 because its all I have available here at home. Attempting real tuning out in the field is a PITA. That and drag on the fletched arrows starts pulling them down out of grouping with the bare shafts.