She said AN INCH not like 3 feet. Chill out guys. Hoping you dont mean a foot. Just raise the rail slowly, a little bit per ride. If the horse is only jumping a foot, a little higher is no big deal. If the horse is already jumping 3 feet or more, its a little more risky. It dosent hurt to push a horse a little bit, to get them to their full potential but if hes nocking alot of rails at the current height he might be maxed out.So she is doing it on a dare eh? And she is going to try to make him jump higher than he is comfortable with for just a dare? Poor horse.... all for a dare.
You have to be VERY careful though - My pony used to jump C grade and win, never stopped or ran out - I then went up a grade, only like 3 inches difference, and he was jumping it fine at home, but at the comp it overfaced him and now you can't even get him around a D grade course (half the size) without him stopping....It's an inch. The horse won't break its legs from jumping an extra inch. If anything, it'll just run out or refuse. SillyBunny has good advice.