Maesfen
Extremely Old Nag!
12st 5lbs is the max weight for a point-to-pointer nowadays I believe and they can carry that over 3 miles plus, over fences and at speed. Yes, they are probably just a tad fitter than most of our horses, but some food for thought.....
Yes and they will be a heck of a lot fitter than most other TBs unless they are in racing yards too. They will also be carrying less excess fat than your normal non racing TB even though they might be eating more.
There's also the case for static weight on a horse usually weighs less to them than a moveable object (rider) as the rider can unbalance them so easily unless the rider is super balanced and rides light. I know many TB hunters (admittedly usually of NH breeding rather than flat bred) that regularly carry up to 14 stone or more over all terrains and cope extremely well because they are fit and used to the weight of the rider right from first coming in off grass for fittening.
IME, it is the balance of the rider with an experienced independent seat and good hands that can ride virtually any height or build of horse whatever the rider weighs; it's the unbalanced riders you need to restrict as they will always weigh heavier to the horse however light in weight the rider is.