I am still in the process of building one, I recommend trying to hunt down a decent deck/bulkhead mounted manual bilge pump, some of the eBay ones are only rated to about 25L/min, would be like cycling in low gear up a big hill. A quick look and you can find 55L/min and higher for not much more. I was able to grab one at a garage sale and off the top of my head it's rated something crazy like 105L/min or 120L/min, it's down in the shed, but I know it's crazy high, only paid $20 for it too hehe.
I probably should finish the thing as I just recently grabbed a deep sided classifier off Gumtree for a song specifically for it. It's basically done, just a couple of welds (a small pain in the ass as I have to borrow a Mig/Tig as mine was pinched) and connecting the plumbing. Mats, moss, expanded for the sluice run all ready to go, just need to find some heavier gauge stuff for the header box. I had not bothered with it for a while as I'm starting to think I collect more gear than gold these days. I had the shits last weekend and told the missus I might as well just put it all out of the front lawn "free to a good home" lol.
Copied John Jacob's build pretty much, I have seen a few builds with a rod straight down the middle to break up the side/side action of the water a little and minimise blow outs, or vanes and even "flippers"
http://bedrockorbust.blogspot.com.au/2014/01/more-rocker-box-mods.html
John Jacob's new design
https://www.youtube.com/watch?v=w_VNW2QVIFs&t= video does not want to embed for some reason.