Unless you have a genuine 31" draw, you also have room to pike the bow a little shorter, too.
Hickory will be a lot stronger in tension than your ash is in compression, so once you add the backing, be sure to bevel the sides so that the back of the bow is narrower than the belly. If you were to saw through the limbs bevelled like this, the cross section would not be rectangular, but rather "TRAPEZOIDAL". This is called "trapping the back".
Now having less surface area of back compared to surface area of belly, you are balancing the forces. And you must always use the forces, Luke. Sorry, that slipped out there.
Honestly, though, I would tell you to pike it, go back to early stage tillering and make sure you have zero hinges before tillering it out to whatever weight you then get. Then start afresh.