Arrow weight vs spine vs FOC vs etc.

My method of initial tuning wood or cane arrows of using traditional bows without shelf (i.e. composite or ELB) -

1.) Weigh the arrow without the pile.

i.e. for example Without Pile (WP) = 26.2 grams

2. Increase the arrow weight by a factor of : One gram per holding weight on the fingers (bow poundage)

i.e. for example Holding Weight (HW) = 36.0 grams

3.) Then subtract the (WP) by the (HW)

i.e. 36.0 - 26.4 = 9.4 grams

This gives you an approximate weight of pile

i.e. 9.4 grams = 145 grains

4.) Then adjust for the amount of F.O.C desired . . .