I got everything installed for this setup. I did it how it is pictured. It doesn't look as pretty as the diagram, but you can understand the flow with the diagram. You wouldn't be able to understand the flow looking at all the hoses. It's all installed under the swim deck platform. To gain access, just remove the tray where the clean-out ports are. The clean out tubes are still there, and also in the way quite a bit, but it is what it is. The bags are all the way in the back of the boat in that compartment on the "shelves" that are back there due to the design of the hull. The pumps are mounted to the wall that separates this compartment with the engine compartment.
For the setup: First things first, I've never even tried to surf before so this whole system was installed to keep me busy and entertained through the winter. If it doesn't work very well, I'm not overly concerned. I know there are better ways (and products) to do what I did. I went with a reversible impeller pump. It's a knock-off brand. I got the bags used on ebay. It's a matching pair. They are rectangular, I want to say they were about 36 inches x 12 x 12 or so. I put some tennis balls on the big bolts sticking up in that storage area, and wrapped the bags in the old hydroturf I pulled in preparation for my SeaDek install. I did this to (hopefully) prevent any punctures from bare fiberglass or anything else poking out down there. The intake is down low near the boat's drain plug (facing the side, not the back). The drain port is a thru-hull fitting on the side next to the pre-existing bilge drain (tightening the nut for that thru-hull fitting and putting the tube on that fitting was by far the hardest part of this project for me. Find a small person or a kid to help!). Everything else was just a bunch of hoses and hose clamps. And a few threaded adapters. I used 3/4 inch hose.
Once again, I understand this isn't going to be the most effective or fastest ballast system on the lake. I'm not too concerned about it, really. I also understand the bags aren't going to fill all the way due to the constraints of the compartment. I'm okay with that, too. This should add some weight (even if it's not a lot), it will be hidden, and it's not taking up any additional space in my storage areas. For me, these were my main objectives. I'll probably still have to add some weight in the form of humans to get a big enough wake to surf, but this system will hopefully help.
Everything seems to work when I tested very briefly in the garage (didn't want a huge mess of water in the garage). I had to "prime" the pumps, though. To prime, I just hooked up the garden hose to the inlet of the system. The exhaust will heat things up, but it shouldn't get hot enough to melt anything. The pump motors probably don't like being hot, but I don't expect an extremely long life out of them anyway. As long as I don't have to prime it every time I go out, and as long as the drain doesn't automatically siphon, I feel like this will be "mission accomplished."
I'll try to get some pictures posted in the near future.