I have been meaning to build another rocker box. When I first saw the Allen Tree box with the manual bilge pump I liked the idea and put together a diaphragm pump from stuff from the hardware store. Two sump pump one way valves, some PVC fittings and the business end of a rubber toilet plunger. Worked great until the rubber part cracked.
I have a couple recommendations on the construction of rocker boxes. The removable riffles in the bottom get super stuck in there like shown in Morgan's book, instead of a riffle ladder you can make a string of them with some cord, drill holes in the riffles and string them up with knots inbetween for proper spacing, use the wedges on top of side rails on top of the loose riffles, by this method you can pull it all up and out instead of dragging it tooth and nail out the end. The back end of the side rails can be wedged in the back against the guides for the apron. If you build a mini rocker you might as well install solid permanent block riffles, 2 or 3 is all you need. A big one I discovered is the punch plate in the hopper, a piece of hardware cloth or expanded metal will not work right, it needs to be an actual piece of sheet metal that you have to punch holes in, the holes should be spaced apart about 1.5" or more apart, this retains water longer and facilitates a more thorough wash of the rocks. My first book on prospecting was Morgan's and I love rocking the old school. The apron is the most important part, I like a double sag, the picture in the book does little to help show how it should work and he doesn't really give a very good explanation of how it is supposed to work. It's not a sluice, more like a really tricked out gold pan.