That will also lower the FOC, with the 100gr you have now your FOC is 10.9% with a 75gr head the FOC is 8.1% plus the arrow will still be on the weak side at 65lb.

This is why I start off with a head weight then build the arrow around the head to get the highest FOC I can.

This 10 to 15% that seems to be the industry standard these days is not IMHO the best way to go for the best arrow flight and penetration, you need to get the FOC to atleast 19%.