Our trailer builder welded two angle irons on each side of each fender. A little bit of work, but he cut the material and welded a plate at an angle onto the angle iron, and also welded a cap on the end.
He welded them below the frame at our request so we can have the teardrop sides overlap.
Seems like as good a solution as any. I can stand on the fenders with them mounted this way (3 quarter 20's on each side of each fender). I can get to them to remove the fenders without too much difficulty.
We may regret not paying more attention to how Tony builds his teardrops on a pallet, but we plan to bolt the floor down and then install the sides on the trailer, maneuvering to avoid the tires (although we could take those off, of course) and spare tire holder. If our fit isn't perfect, we have the option to notch the sides of the walls around the fender holders (and spare tire holder) by an eighth inch or so.
Tom