I am shooting FMJ 340 spine 27.5inch shaft with a lighted nock, 125 grain and 50 grain hit insert with my 65# bow at 29in draw length. My current FOC is 13%. I am hoping to augment my FOC some, get it around 15-18%, by using 75 grain inserts instead. Any thoughts on whether i need a tougher spine arrow to add the extra 25 grain to the insert or should the 340 work ok?