Toy Hauler Frames

Most 5th wheel toy haulers in that range have a 10-12" I-beam but not like one used in construction, these have only 2.5-3" flanges and are much lighter in lbs per foot than a normal I-beams. As long as you have enough truck don't worry about weight and build one that is heavier than you think you need, definitely don't skimp there. On a bumper pull I think most are in the 8-10" range. If you look at a bare frame used on even the larger toyhaulers before they start building the box on them, its kinda scary how they are able to hold the weight they are rated for. They wiggle and wobble, sway back and forth and just feel really flimsy. If I were building one personally, I would start with a gooseneck or a deck over bumper pull as they are substantially built and build the box from there. I think by the time you try and rebuild your TT to the specs you need, you'd be better off buying a built deck over trailer and starting your build from there. Don't try and reinvent the wheel so to speak.