I want to extend the bumper on my AF 22GQ so I can carry the generator and other stuff. The spare tire will be relocated. The extension will be made of 3" square tubing and will be bolted and welded to the frame. I'll cut the bumper off and reweld it to the ends of the extensions. I estimate there will be no more than 300 lbs. on the extension. How much tubing must extend into the existing frame channel so as not to overly stress it and risk breakage? Thanks for any insights.

Jim