I can't answer because I don't know how far off you are, not how far the spokes can stick up before running out of thread. Before you throw up your hands in disgust and take it apart, thread one nipple down a spoke and find out how far your spokes can potrude, and compare it to your expected build. I'd say you want a safety margin of at least 1mm, but if it looks close, you have a decision to make, whether to gamble your time in completing the wheel, or start fresh.