^^ If weight is the most important factor - which a 20% rule would imply - then using a 12 lb jump saddle like my old Bates CC would be better than using my 35 lb roping saddle. But if saddle fit and weight distribution are important, then using a saddle that spreads my weight over a larger area AND that keeps it further away from the spine than my Bates CC is worthwhile.
When we simplify things down to "20% OK", we simplify things to the point we are wrong. Since this is one of the most frequently asked questions on HF, why not create a checklist of things, such as (no order intended):
Saddle fit is even more important for a heavy rider than a light one.
Thick legs and good feet are critical for a heavier rider.
Thicker legs on a lighter horse will help more than just getting a bigger, heavier horse.
Riding balanced is important, but straight lines & gentle stops are too.
If you are worried about your weight on your horse, let your horse pick the pace.
I hate the phrase "Just a trail horse". But for a heavier rider, walking on trails may beat the tar out of doing arena games/dressage/etc.
Short back/thick loin good, long slender back bad.
Get your horse in shape gradually.
Rider weight IS relevant. It just isn't as relevant as some women seem to think...because very few guys think that way. We can't afford to...
What should be on a list could be debated. But it seems to me a short list of 5-10 guidelines would be far more helpful than the commonly suggested 20% rule. We should encourage folks to look at the total picture.
Surely I'm not the only guy with a preference for slender Arabians who finds they can do a floaty trot under me even though I break the 20% rule all the time! When the most commonly accepted guidance on the Internet says my horses all struggle with me every ride, and that most guys ought to quit riding horses and buy ATVs...well, it ****es me off. Not anyone here personally...just a frustration with the idea we all need to be either slender gals or ride big heavy warmbloods. My biggest horse probably weighs 850. I'm not planning on replacing them with some big quarter horses or warmbloods any time soon.
Bandit is the sort of horse I'm supposed to avoid - too slender for 160 lbs of rider plus 35 lbs of saddle. I'm glad he doesn't have Internet access, or he might feel obligated to act tired at the end of a ride.