Looks good!
James, it's sitting on top of the top mount plate, which goes from frame rail to frame rail, and is 6.5" deep and .179" thick. What I do to my winch bumpers, which I suggest adding, is a 1" tall strip or 1" piece of tube across the back, for rigidity. Also, instead of just the cutouts at the sides of the winch, you might cut a couple pieces of steel like shown below, to close up the sides of the winch box.
And wow, that's the reason I use a texture gloss black powdercoat! Matte black or texture black hides a lot of the sanding marks and stuff, but gloss black just makes every little bump and undulation stick out. If you're going to paint something fabricated in a gloss black, you should probably skim-coat (you see them doing that to the fabricated frames/tanks/body panels on the "chopper" shows and stuff, as well as show cars and any body repair, before they paint them.) it with bondo before paint.... but that's neither there or there...
Mike
ETA: Better views of how it's built...