How big is big enough? From a biomechanical point of view, 16.2 is plenty of height and too much for many animals, and plenty of great horses never got close to that size.
With increased size comes increased need for greater energy, slightly larger (and denser) bone to carry the increased weight, and better balance to move the horse efficiently.
Yet today, as in times past, the bigger a yearling is, the better it sells. This is apparently a human inclination, and reason is our only aid in calming the notion that bigger is better. It is nothing new.
For instance, Vigilant, in the London Sportsman of 13 June 1903, wrote:
It is surprising how people, and presumably good judges too, hanker after size in horses. A big yearling has always a better chance of making a fair price than has a medium-sized one, and in estimating the prospects of supposed Derby horses, we are constantly told that so and so has not grown, as if more growth were the be-all and end-all of a racehorse. The truism that a good big one is better than a good little one is repeated … [with] … no suggestion of the vital fact that good big ones are extraordinarily scarce, while good little ones are pretty numerous, and unless we are well aware of this we are almost sure to go astray if we compare horses by size along and give the bigger ones indiscriminately the preference.
I am led to write on this subject by having seen so many statements that Rock Sand does not fill the eye as a Derby winner should, the meaning, as I presume, being that he has not the size and range of an Ard Patrick or an Ormonde, a Persimmon, a Galtee More, or shall we say a Jeddah.
Well, but the same people who say or write these things will also be telling us at another time that medium-sized, short-coupled horses are the most suitable for the Epsom turns and gradients, and that one like Ard Patrick, for example, would be more at home on the Town Moor at Doncaster.
The truth, however, appears to be that a good horse finds all courses pretty suitable, and that, within certain limits, the size of the animal does not make a difference. … The stable estimate of Rock Sand is that he stands 15.3, and that this is an amply sufficient height for a Derby winner, there are abundant records to prove. Taking the two successive years 1867 and 1868, we find that the Derby winners Hermit and Blue Gown were, if anything, below the 15.3 standard — indeed, I doubt if Blue Gown stood more than 15.2, and he was even shorter in his forehand than Rock Sand.
Rock Sand not only won the Derby at Epsom but also the English Triple Crown and, after his importation to the States to stand at August Belmont’s Nursery Stud for a time, sired many top-class horses, as well as the dam of Man o’ War.
Size today is much the same as it was a century ago: medium is better and yet subordinate to the quality and talent of the athlete.