My K-Mag (LH 55#@28") shoots sweet at a brace height of 8.5" (measured from the grip) and a nock point of +3/8" (I shoot 3 Under). I draw 28.5"-29", with a 525 grain arrow I'm getting 180 FPS.
One thing about my K-Mag, it does stack. I can tell the second I pass 28" on the draw, as the stack begins immediately. At 30.5" draw, I bet you will experience a lot of stack...