Frank V, I'll tell on myself...I get lazy occasionally especially thinking my 40+ years of shooting will tell me what's wrong by "eyeball".
A while back I was setting up some wood arrows to a new bow. They seemed by eyeball to like 145 tips. I wanted to shoot WW's (for elk) but they are only 125 so I put 20grs of lead inside with a short taper..They were flying good and grouping well, but about 1 out of every 5 to 10 shots I'd get a "flyer" about 6-8" right (I'm right handed)...It was never the same arrow so it wasn't a BH alignment problem. I just chalked it up to "me" screwing up a release or torqueing the bow...Later on I decided to use Snuffers for deer and slapped some 145gr Snuffers on..Whoa! THEY ALL grouped a foot or more right of the field tips...They were underspined with 145 tips. I took the 20grs out of the WW's, went to 125 Snuffers and field tips...All my "flyers" went away.
Moral of the story, you can't tell by eyeball with field tips or narrow broadheads. They can "look" fine but your groups are going to be bigger then they should be and when we do screw up, you're going to miss further then you should if you aren't perfectly tuned. Wide broadheads tell you exactly what's wrong if you know what to look for. The bare shaft planing method does the exact same thing. Many of us just chalk up what we see as being our screw up instead of understanding we might not be as well tuned as we think. Had I hunted with those WW's without straightening out my tuning, I might have got one of the "good" shots instead of the "flyer". But I might also have screwed up a release and or got caught in a rain storm with wet feathers. The best thing would be a miss, the worse a wounded critter.
As for being a good shot and shooting good groups, any one of us, take a target say 24"x24" with our field tips and start backing up till we can barely keep all our arrows on the target. That might be 20 yards for some or 80 for others. Whatever that distance is, it can't be considered a "good group". Start mixing in either bare shafts or wide Bh's like the Snuffers...If you aren't well tuned, you won't keep many if any of them on the target...Which way they miss tells us exactly whats wrong..Make adjustments till you keep them all on the target and you are golden! That's the planning method in a nut shell. Group size is relative. Good tuning won't stop us from missing, it just keeps us from missing as far! If makes our arrows shoot flatter and penetrate better. No down side to doing the best we can...
....O.L.