I tried that way a couple of times - pics are somewhere here on the forum. Same gripes as Pete. Also, I had to hang them upside down, and when I got a little impatient with the varnish, i.e. brushed on too much, the drips ended up on the tops of the coamings where they had to be sanded because they were quite visible.
Then, at A-231 Bill's suggestion, I started doing them this way. I drilled a hole in the top of the 4x4's to accept the bolt from the winch bases. Works pretty good. They're solid enough to brush on the varnish and you can get at all the sides and edges. With the different heights, you can also rotate either of them to get better lighting. Also, with the coamings upright, the drips move in the right direction...