Some things to keep in mind as you are deciding where to remove some hair from your horse:
Where does he sweat? Common areas to create some air conditioning for the sweaty horse include under the neck, around the flank, and in between legs. Your horse will also sweat in the saddle area, but it may be best to leave this hair so your tack isn’t in direct contact with his super short hair. A sweaty saddle area is much easier to dry than your entire horse. A fleece cooler usually does the trick to dry the saddle area as you groom after exercise.
Can you effectively use a blanket to make up for the air conditioning that your horse needs? If he has some significant air conditioning clipped in, a blanket will be needed. But – you may find then that some hairy parts remain too warm under the blanket. In this case, opt for a clip that removes more hair over the parts your blanket will cover.
You can also vary the length of the hair that remains after you clip your horse using blades that leave 3 mm of hair instead of 1.8 mm of hair. Also use clipper guards to take just some off the top, as the saying goes. Remember that it grows back, and if you start out clipping some off and it’s not enough, you can always come back and remove just a little more with a different blade or a different guard.