ok from what I can tell in the pic,, that is the spot that might be a bit thin,,
just a suggestion,, take wood of the outers and toward the handle before you remove any wood there,,,
even if you heat treated,, ok but if that spot of the taper is too thin,, it might be a problem,, or is indicating that the limbs are not bending even,,
if we could see the bend of the bow, ,it would be easier to tell where it might be over stressed,,
the tiller would indicate if that part of the bow was working too hard in relation to the rest of the limb,,
but at this point I am really guessing with not enough info,,