I have STi2 4-GW, Dri Tac LT 41 gr. Grips, and I would like to build a set of irons @ D2 swing weight using the Pro 63i shafts that weighs in at 63g. The estimated SW without tip weighting is about C4, how much tip weight would I need to reach D2. Thanks for any input

Answered question

Others may have more insight to this, so I’m just leaving a comment…
from the info you provided, you would need to add 16 grams!
I believe you are using total weight for the shaft (uncut) if that’s the case, the weight and length would be less.
Assuming a 7 iron length, I calculate the following:
7 Iron length 37.25″
Raw shaft length at 40.5″
Raw shaft weight at 63 grams
Headweight 267 grams
Grip weight 41 grams
I calculate a SW right at D2