LOL, you shouldn't have to worry about seeking out drafts or crosses. There are tons of standard stock horses out there that will fit you. The percentage is a good rule of thumb but there are also variables to consider. If there are 2 horses that are the same height and weigh the same but one of them has a short back, short legs with big bones, big feet, and a broad chest, then they would be more capable of carrying a larger rider for longer distances than one who was built like your typical thoroughbred, narrow with stick legs.
Also, it depends on how good of a rider you are. A good rider who weighs 250 is easier on horses than a bad rider who weighs 100.
In all honesty, I've got a horse that stands about 14.3 and weighs just over 1000 that could carry you all day and still have a spring in his step at the end of it just because he's stocky and thick but I have a 16 hand TB that weighs about the same that would be dragging halfway through the day.
The way I see it, if you feel comfortable on the horse and they don't show any signs of having difficulty carrying you, then that is a good size horse for you.