OK, truth, fitness is more important than weight, the fitter you are the better rider you are, so it helps to work on that.....not at the moment though, I know what multiple broken and cracked ribs feel like.
As the weight, well I guess I would be lying if I said that I didn't think it had an affect on stability, but does it have an affect on injury, who knows?
I am a plus size rider, and in 2013 I took 2 falls, one was not due to my weight, but my inexperience, and an over the top reaction from my horse, was trying a trot/canter transition, and I caught him in the mouth, he responded by broncing, and I came off over his shoulder, kind bounced, just lost some skin, picked up some bruises, but got back on and rode him, just walk and trot.
One week later, I went to get on him again, was standing on a mounting block, put foot in stirrup, felt saddle slip....could be weight related
not sure what happened, but I woke up with the ambulance there, as they got me out of what was later described as "the impact crater" I don't honestly know if my weight contributed to that, or the height that he sent me, and the speed that I hit....and I was badly broken.
After that I started riding in a safety vest, and I fell off wearing it last year, I think my weight did contribute to that fall, I was already leaning forward and down when he spooked, and I could not recover it, but the vest meant I bounced.
My current mare, she is spooky, but so far the worst that has happened is I have lost my stirrups, but I have stayed with her every time, but she is a very honest girl, she spooks, then she realises that I am off balance, so she moves back under me, love her.