Here's what I think of arrow tuning. I'm gonna say it....and admit that I'm a trad "novice". Hopefully someone will set me straight if I'm wrong.
FIRST thing I'd do is figure out what size (grain) BH I wanted to use. Second, I'd take that into consideration in determinin proper spine. Next I'd start with a full length arrow. If it's too stiff (with the grain FP you wanna use) you're done. If it's too weak, you can start trimming.
Now...you CAN add brass weights in if you're too stiff (initially), but I've learned first-hand that they affect tuning more than just the amt. they weigh. An arrow with a 100gr. brass insert and a 100gr. field point will NOT react exactly like an arrow of identical weight/length (utilizing a heavier point) arrow. Weird, huh?
Lots of ways to skin a cat, but "I" like starting with the weight BH I wanna utilize.