to predict a yearlings full height, measure legs, hold one end of a string at the point of elbow and pull the other end straight down to fetlock, keeping your hand at the elbow bring the fetlock end of the string up and above the withers, then add another inch to see how high future withers will be, for a foal about approx 2 inchs. i have uased this method for lots of years, it is from an old american idaho horsewoman.