FLHunter and I disagree on some aspects of the FOC topic, I contend and many FITA shooters would contend(I believe McKinney has documented it) that a low FOC hurts performance in wind at those 70 and 90 meter distances especially on light arrows. From the side FOC helps the arrow act like a weathervane and steer somewhat back into the wind or at least keep better on track.

Higher FOC also lowers the drag of the arrow, this may seem backwards at first, however the FOC helps keep the arrow shaft movement in line with the path of the arrow, by keeping the nose pointing in th edirection of gravity. Due to gravity, all arrows will follow a parabolic curve after launch, a low FOC will tend to be more nose-up(at extreme ends of the normal range), this causes the arrow shaft to be traveling at an angle to the arrow path(using it somewhat as a lifting body). Flight arrows use this effect to get more distance, typically very low FOC even zero the way we normally calculate it, but penetration if required would certainly suffer.