Justin's right. It is pretty short for a first time, PLUS, even experienced bowyers often start out with a longer bow than they want/need, and if it turns out good, then shorten it and sand or scrape it lightly to the length/poundage they want. You would be well-advised to at least start 6-12 inches longer and then shorten it if you absolutely have to. But ake sure the 68" turns out good before you hack it down to 58'. There are many ways to mess a bow up even if you've done it for 10 years, and you'll wish you had that extra length to fall back on.
Good thing you pointed that out Justin.
~~Papa Matt