Nothing wrong with mounting this way.
Do pay attention to the mounting of the bumper to the frame.

My winch is mounted on a 2" box tube that bolts up under the frame rails. This uses one 12mm bolt on each end going up through existing holes in the main rails of the frame. The bolts are in single shear and have proven reliable.
You just want to make sure the front horns of the frame want the loads of the winch. I expect you will not have problems with the frame though.
You may want to add a doubler across the inner face of the bumper and I would try to have these attached to the frame also.