I've heard of a few people beefing up the frame extension to handle a heavier duty hitch, but never heard any long term reports on the success of it. Most welding shops won't want to touch the job for liability reasons, but maybe you can find some big shop that has insurance for that sort of thing. For sure you can find a shade tree welder who will do it, but you will never know if his mods are good, safe engineering or just good-looking pieces of extra metal. Shop carefully!
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL