Brian,
Putting your set-up on OT2, I used a Katera because the specs are about the same, at your DL 27.5 and 68#'s if you use a 28" GT 5575 and a 125gr BH/FP you'll have right close to a 390gr set-up, with a near perfect spine, FOC of 12.15%. Still keeping you in a good high 280's speed range with LOTS of energy behind it, 72ft/# off the rest, and maintaining 65ft/#'s at 45yds. Drop to 350, and you start out at 68 and drop to 62. But other things to take into consideration are the vibration the bow has to absorb if the arrow isn't absorbing it all, which will create noise, loosen up attachements to the bow (sight, stab, etc).