Bare shaft tuning

[Talon]

I've tried various nock positions Tartar and I like to tie my nocking points with serving thread (I'm not a big fan of crimp on nocks).Still can't get a perfect flat bare tuned shaft.
They strangely enough do straighten up a little bit more when shot perfectly vertical and the arrow nocked 1/4 below horizontal.I can't grasp why,but it's irrelevant as I always shoot my bow with a bit of cant to it.About 2 o'clock or thereabouts.Forgot to mention I also shoot off the shelf with a felt pad as I like the arrow as close to my hand as I can get it.
Using 3"" feathers fixes the nock high issue.I haven't tried my current set up with broadheads,I imagine I would have to go with a bigger vane as the ones I'm using are only a 1/2 "" high,they give good flight with my field points