Are you asking how to know when it's safe to let him run in the woods, without unnecessary fear that he'll just run away?
I'm of the type of person who uses probably more caution than most, since I'm always afraid of losing my dog. I get to know my dog real well, become friends with him so that he wants to be around me, and I also know what his body language says. Of course I also teach the "come" command thoroughly. Once I feel reasonably confident I just unclip the leash and hope for the best
I do that with any dog, hound or not. I have one hound whose leash I'll never unclip again, and three other dogs (one hound, two other breeds) who I am perfectly comfortable with unleashing.
Good luck, hope it turns out well, however that may be. I believe in just taking it slow and steady.