Krusty,
Cant say about hickory.....but I steam bend walnut, elm, and ash. Have done some of those 2 & 3 times with no ill effects. As a matter of fact I sometimes bend the bows twice, on purpose, to get exact bend that I want if it's severe. Dont have hickory but elm might be close to it, and I did not hurt it......hope that helps some.
rich