RE: foc(8 to 12)heavier or lighter or in between?
Howler,
Try going to 4, or 5 inch feathers. That will help your FOC, and as long as it doesn't lighten up your arrows too much for your liking, than you should be fine.
This is where a GOOD pro shop comes in handy. Stop in and see them, and have them help you compute all of your options until you come up with a perfectly matched arrow!