I am shooting a 06 trykon set at 70 pounds at 27inches. {yeah I know I got stubby arms}. I am flinging 3-39 A/C/C arrows cut to 25.5 inches with a half out making a total arrow length of 26 inches. I am using a 100 grain point. I am also using a release and dropaway rest. I have been struggling with a stiff spine reaction while tuneing my bow. I can get it to paper tune and bareshaft tune. Only my rest is adj way left and higher than I think it should be. {I am right handed} I am going to get some 125 grain points to try today. If this softens the spine some, should I expect better groups with my arrows also? If I can get it tune tune a little better? Also how much will 25 grains slow my arrow down? I could just get another doz weaker spine arrows. But I already got a doz 3-39 and would like to make em work if I can.
from what i understand, for every 3 gr. your arrow is above IBO specs (350 gr.) you will lose ~1-2 fps. So around 8 fps.