Here's my two cents....I've made quite a bit of locust bows as well,and I've used locust from Michigan,Indiana,Ohio,Pennsylvania, and soon to be North Carolina(ruling out specific geographics are weaker than others) and I have yet to experience any fretting issues with black locust....the key is proper execution of correct design with seasoned wood ...simple as that....if your getting frets all along the whole limb its locusts way of telling you that your design is incorrect and not wide or long enough or both...if its localized to certain areas then you have a hinge there of some sort and the load is not evenly distributed well enough thru out the whole limb....I've used locust that came from the same tree that two other well known and accomplished bowyers(won't say names) that they experienced fretting all along there limbs and mine did not,yet they came from the same tree...again its locusts way of saying I wasn't designed correctly...but those guys will tell you the woods junk
and locust will handle high stressed designs if the limbs are made wide and thin enough...locust loves to be wide thinned limbs....another important step in the building process is tempering locust...but you have to be careful of not to over cook it and turn the belly to dark..it can make the wood brittle and tension weak so to say...I like to temper it just past once it turns color then move onto the next spot...
If made right locust makes a mean casting bow,with excellent early string tension and bend resistance,which is one of my favorite properties of the wood...I love a piece of wood that wants to fight me back as I pull it
Black locust has been and still is my second favorite wood,and rightfully so