Straightarrow

I make my decision based on what draw weight and spine arrow I' m using. If you decrease the tip weight, then the spine is stiffened. If you were shooting the perfect spine previously, you will now have to raise the draw weight to compensate for the stiffer spine. All this is critical when shooting broadheads. You have a wider acceptable range of spine when shooting field tips, especially out of a well tuned bow with level nock travel. Bare shaft tuning is how I determine proper spine.