Is there a good conformation shot of your mare available to us?
Honestly, while a stallion might produce nice offspring, the end result with your mare will certainly be, at least partly, effected by her.
My next question is what do you want to do with the foal? That would be a major factor in whether this stallion is going to produce what you'd like.
If you're in communication with the owners, could you get your hands on conformation shot (or 4) of him? You can't just look at the offspring he produces, because, as I just mentioned, the mare has something to do with that as well. To have an "idea" of what is coming from him and what comes from the mare, a shot of each of the mares he's been bred to would really help, along with good photos of the foals.