It depends on what you want to use the foal for. Do you want one that is taller or shorter than the dam? I've seen people use mini horses on 13hand mares and 15.3 horses on 13 hand mares. The foal grows to accomadate the size of the mare and complications from a foal growing too big because of the stallion is not common at all.
On another thought personally I would feel really sketchy breeding a 17 year old mare that has only had one foal.