Tempest blanket hood sizes?

Looking into getting a new winter turnout with a hood. There’s a sale on the tempest plus 1200 D 300g neck attachment and winter turnout, but I don’t know what size to buy the hood.

My guy usually wears an 80 blanket, so im going with the 81 (choices are either a 78 or 81… I figure bigger is better than too small.). I’m not sure what size to get the hood though… I can either go with a medium or large.

Horse is 16.3hh Oldenburg/Thoroughbred/Hanoverian.