Damn 12" seems huge! If I can lay a 29" tire with 1.5" over the stock rail probably with room to spare, to lay a 32" tire should only take another 1.5" max notch height which only puts it at 8 1/4" . The biggest tire I would run is prob a 265/40/22, really don't have much intention of going any bigger wheels. But I'm if that time ever comes I'll just lay another piece of tube across the top weld it up and cut out the middle. The curvature on the tubing corners will create a natural bevel, giving lots of penetration.