FWIW,
I got a 1/2 doz test kit from magnus of Turkey Flight Traditional. The test kit was made up 29" BOP, 125gr heads, and 4" shield fletching spined 40, 44, 46, 49, 53, 55.
The 49# flew the best from my Dave Johnson longbow. With the 46 and 53 I saw different flight and arrow wobble after many shots downrange. The 49# was spot on. I PM'd Matt and asked him to make me a 1/2 doz of his poplar shaft arrows spined 48-50 range. He made them up all spined at 49. The arrows arrived and I put 125gr Magnus 2 blades on them and went to the BH target. Flight was near perfect. I switched the arrow on the string to cock feather in and now they fly perfectly.
I am not a great shooter, but I am picky about an arrow's flight from the bow that has no wobble. Magnus at Turkey Flight Traditional gave me those arrows.
Thanks Matt.