I am one of those guys that believes most folks seriously overthink their arrows....and specially true regarding selfbows. With most selfbows, archers paradox is your friend. Arrows are "spined" so that shooters know "where" they are beginning in regard to stiffness of their arrows matching the poundage they are shooting. If you shoot 55lbs@28, or very close to that...then pick arrows that are spined to reflect the poundage you shoot. Simple.
Shoot enough feather to help your arrow correct itself quickly. Simple.
Shoot a consistent weight up front....anywhere from 125gr, to 200gr, it doesn't matter, but know that as you approach heavier up front, it MAY affect your spine some.
Don't fuss with the length of your arrows. Really? If you want to shoot consistently, keep your arrows the same length all the time. Most of us shoot some form of instinctive/learned style, in which we "see" the arrow (admit it or not) and messing with length will mess with your ability to be accurate, IMO. Simple.
With any trad bow, you should be able to achieve great arrow flight with arrows spined to match the weight you draw (with small adjustments to spine, depending on point weight, drawlength, etc.)
Little things like brace height, nock point, tiller, sloppy release....none of those are the fault of the arrow. Fix that stuff.
I constantly see posts that go on forever about arrow tuning....okay, I get it for those who like that stuff. No problems there. But if you are like me, and hate to constantly worry about details...stick to the basics. Learn about them, they should be second nature for any trad bowhunter/shooter, and should be the rules that guide you first and foremost.
I have been building selfbows for nearly 30 years now....and shoot upwards of half a dozen bows each year...with little problems when I stick to these rules. I shoot to practice hunting...so I'm not a long range guy. I never bareshaft...whats the point there (to me). I aint gonna hunt bareshaft. I shoot plenty of feather to straighten out the arrow quickly, for accuracy, for penetration purposes, for clean flight through unknown terrain....It hasn't failed me yet. Most bows I build for myself (since I don't sell them) and in nearly 30 years, I can't say that I ever have had to adjust my spine more than a single spine group up or down to get good (perfect) flight - not more than a half-dozen times (remember that is for a hundred plus bows...and each one is different).
Stick to the basic rules...keep it simple.