Much to my surprise, I have discovered that the horses of Medieval England did not reach the size that I have published in GPC.
Sure, some of the breeds existed, but according to
The Medieval Horse and Its Equipment; c. 1150-c. 1450; John Clark; Boydell Press, 1995, 2004
horses stopped getting larger and larger about during the Tournament Period.
Thus, should we be blessed enough to see such an event, any future editions of GPC will have horses no larger than 8d6 damage.

Correct. The huge draft horses of later eras were bred for pulling heavy stuff. Even the "great horse" of the medieval period is not as large as, say, a percheron or a Shire horse.


T.