Hi,
the hackberry that I've cut in spring took a lot of reflex when reduced green to 1" deep at handle area to 3/5 at tips. So, if you don't want so much reflex, let more wood on the stave. (Hackberry here is celtis australis, the european one...I live in Spain). And if dried enough, and wide enought, it will make a good bow, sure!
David