If you are accurate and his real index is a 7, and he consistently keeps it at a 10, I'd tell the president why I'm not inviting him. It sounds like he's been doing this for years, so it's time someone should call him out on it. I'm surprised he's still allowed in any game or tournament if he consistently shoots under his handicap in tournaments. All the clubs I've been at sniff out those sandbaggers, and they either have their index adjusted or are not included in anything.
It's a crappy position for you to be in, and if he's a cheater, he will likely not react well to being called out for it.
It's a crappy position for you to be in, and if he's a cheater, he will likely not react well to being called out for it.