Doesn't look too bad. If you need a guide, I did find this on a google search :
Be Sure Your Horse Measures Up
The U.S. Calvary published “The Cavalry Manual of Horse Management”, by Frederick L. Devereux, Jr., in 1941. He recommended that the collective weight of rider and gear not exceed 20% of the total weight of the horse. These were horses in top condition whose riders’ very lives depended on the horse's ability to carry them long miles, often at speed. It stands to reason that if they were to incorporate a margin of error, it would be on the side of the horse being overly capable of carrying its rider, rather than less so.
Comparably, a study of 374 competitive trail riding horses compared horse/rider weight relationships. They concluded that these horses can easily carry over 30% of their body weight for 100 miles and not only compete, but compete well. As would be expected, good body condition and bone structure were found to be paramount. Bone structure was evaluated using the front leg cannon bones as representative of general structure.
Measurement Test
1. Add up the total weight of the horse, rider and tack. (See TGH Summer 1998, page 37.)
Our example: Damascus, Lady + tack = 1188 pounds.
2. Measure the circumference of the cannon bone midway between the knee and fetlock.
Our example: Damascus, 7.5 inches.
3. Divide this total weight by the circumference.
Our example: 1188 ÷ 7.5 = 158.4
3. Divide the result by two.
Our example: 158.4 ÷ 2 = 79.2
Values near 75 are great, below 75, even better. Values from 75/80 are acceptable. Values over 80 indicate weaker legs and a need to train carefully, especially downhill. Values over 85 suggest you need a horse with more substance.
Damascus rates near the end of the acceptable range, but should still be able to carry Lady in style, comfortably.
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