Yes, lighter is better, but no one has
addressed the training issues that are key to a horse carrying a heavier
rider. You can help them immensely by doing gymnastics to strengthen their
abs (and back muscles) and teaching them to round up and carry themselves
properly.
I have a range of horses here from 13.3
to 15hh and over the last ten years and two kids have ranged in my own weight
between 135 and 210. I've noticed much more a difference/(disadvantage at
the higher end) on my fitness and balance than any real difference in the horses
seeming ability to carry me. I'm about 170 w/tack now and don't think
twice about taking the pony out for several hours. She's stout, about 900
(on a scale, not a tape) so I'm not out of her 20% (if I can do math before
coffee, which is questionable), but she's carried heavier riders without and
signs of distress. by signs of distress I look for her to hollow her back,
fuss and dance either standing still or on inclines, that sort of thing.
so how about some training discussion on
how to help the horse as well as the rider, instead of rider-bashing.
cavelletti anyone? butt-scrunches? belly-lifts?