I always bred the Arabs at two to foal at three. I never did have a mare have any problem working out exactly what she had had, and I think that is only first foal syndrome anyway. I prefer to breed at three now, to foal at four, and, again, have never had any problems with this in the Minis, either. The thing you must bear in mind though is that Minis definitely have more foaling problems that Biggies, and you cannot get away form this fact. Leaving them later makes no difference to this, either, as the pelvic girdle bones become less "elastic" after time and have more problem passing a foal through. Every foal is a risk, no matter what age the mare. I will not breed form a mare under 30" and, even at 32" I will look at her carefully before breeding her. I think, honestly, that height and conformation are as important as age.