I think I saw it mentioned on here before how to calculate the ideal/best spine etc...for your setup?

I'm not new to archery, but new to all these figures and numbers and what is best etc...

My draw length is 28"
current draw weight 63lbs, would like to become comfortable at 70lbs.
shooting 100gr broadheads.

have a few different arrow setups
don't know exact arrow weights...
1 set is 10gr/in estimated wt... 418grs
2 set is 7.9gr/in.................... 353
3 set is 6.4gr/in................... 307grs

Mainly trying to figure out if I could tweak my setup to shoot even tigher groups by determing an ideal BH weight, and or ideal spine/arrow weight etc...

Is spine just arrow shaft diamter? and what is spine used to determine...?

Thanks.