I prefer my bows at least 66" long, at least for selfbows. I've made a couple short hickory bows (working recurves) that were 56" long, Jay Massey style. Hickory isn't as elastic as Osage and what not, and like other white woods is best (as a selfbow) when it's longer.
If you have your heart set on a 60" hickory, a deflexed working recurve would probabaly be your best bet.