For my arrows, I won't go very much below 10% FOC with broadheads. I've shot as high as 15% on wood arrows with 180 grain heads and they did great out to 25 yards, but did start nosediving around 30. In my opinion, it's worse to go too light with FOC than it is to go heavy because too little nose weight will let the arrow 'float' with poor stability.

You'd probably be okay at 9%, but it it was me, there would be 100 grain heads on those arrows to get closer to 10%.