We only put our horses out for an hour or two each day after they've ridden and only in good weather. We've got an old pony with laminitis so she has to wear a muzzle and the grass is quite luscious so only a few hours at the most for our's.
I know! I've seen a few large people competing on dainty ponies. It's not nice when they have a heavy seat because you can constantly hear them slamming in the seat. But I know there are quite a few talented larger riders; Which partially solves the problem.
Ouch! I know someone who broke their neck, still alive and all. Apparently it's very painful - he's certainly lucky! He didn't really break his neck though; he just needed three vertebraes re-aligning - Is vertebrae meant to have an 's' on the end? - not sure