There really isn't a weight limit for trail riding. What ever your horse is comfortable with. I can't remember, do you have the light cordura saddles or regular leather western saddle? The synthetic ones weigh about 20lbs give or take and the leather ones sometimes run up to 40lbs, I think that's about what my Billy Cook is.I wouldn't want to add another 40-50 lbs of weight but then when I think about it, Bob weighs 100 lbs more than I do, and the same horse will carry both of us equally well. Well, I'm not sure Dusty is thrilled with carrying his weight but she doesn't have a problem with it :)
My western is 18 pds. My husband doesn't liie his and is giving it to me also. About 32lbs. I lost 2.6 last week so maybe I should use that as my guide. The more I lose the more I can carry:') I weighed my back pack . It's 17 lbs right now. I usually start out with 2 bottles of water that aren't in there right though.