RE: re-tune?
Back in June, I tried some arrows that were 100 grains heavier than what the bow was tuned for and set up to shoot. I found that I needed to use the 30 yard pin for 20 yards, with the 507 grain arrows. Tuning was OK, though - probably because the spine was still correct for this bow. This might not be true in all cases though . . . . . .