Adding weight to the front end of the arrow and/or reducing weight on the tail end does increase your FOC, so changing to lighter vanes will help. Switching to feathers would do a lot more because they are much lighter than even the lightest vanes.

Changing to 125 gn tips should jack your FOC up to around 10%. If you want more FOC, then add more weight up front or lighten the load in the rear.

Dr. Ed Ashby is doing a new arrow lethality study on Asian buffalo in Australia. It's still in it's early stages because the study is going to run for several more years but some of his early findings are interesting. Such as arrows with extremely high FOC (20% +) are showing significantly better penetration than arrows with more normal FOC's.