Katman, I might have missed it but didn't think I saw you set up specs. I shoot such light stuff that I'm always using 600s, 700s and even 800s. Your title "perfectly stiff tune" kind of rings with me. After shooting a doe this year with excellent penetration using my Toelke 10X Whip 42#28 (40 at my draw) and Axis 700s cut to 27.5" with 175 up front, I did what I usually do---start messing with arrows. Anyhow I played with some fletched black eagle 500s that I had already cut and fletched sitting around. They had 100 grain outserts and I was using 125 stingers for 534 total grains. Without a bareshaft I decided to just tune the old fashioned way---got my broadhead and field point hitting to the same point out to 30 yards. Good enough? Right? Well I shot a buck with that set up---made a poor shot and spined him, my follow up arrow went through a rib and almost made it out the other side---fletchings hung a bit, but he was on the ground at that point so there was arrow ground contact.
So, I guess that set up worked well enough. I figured--forget the bareshaft from now on, but that lasted all of two days... always messing with stuff I stripped the feathers on the shaft that went through the buck and sent a bareshaft down range at 20 yards. The shaft showed very stiff. Not even close to a decent tune. It makes me wonder what I lost in that arrow's overall performance with the feathers working to correct that tune, not to mention forgiveness for a bad release. I'm thankful that it worked out, but I should have known better than to roll the dice by skipping steps in my tuning process.
I spent another day playing with arrows and came up with an excellent bareshaft/fletched group at 30 yards using 800s cut to 27.5 with 200 grains up front. I've added slo-mo video of bareshaft with camera at the target to get close in my barn and then move out to 20-30 yards as usual. I don't think I will forget the bareshaft again as for me it has been the only reliable way for me to tune. I would agree that there are a number of folks that are overspined, but I seldom see someone shooting an arrow that is underspined.