Hi Jason,
I run a Glind shower, which is basically the same thing. Biggest thing to remember is to run the different liquids in different directions through the exchanger. IE, if your coolant runs left-to-right, pump your fresh water right-to-left. Makes it heaps hotter (which I'm told is something you people down south want).
I really don't think there's much more to it than that.
I run the big flowjet pump, and find it does a fantastic job. So much so that I've had to modify the showerhead so that it doesn't use as much water. I was originally going to go for the smaller pump, and still feel that it would do a more than sufficient job whilst being easier to find a spot for. The big pump can draw water from 10m below, but we never have a hose long enough to throw in the river so end up pumping from a bucket hanging from the bullbar. The only reason we went the big pump is because they'd sold out of the little ones and offered us the big one for nothing. It really does blast the dirt/sand off you
.
Hose-wise, I just measured up each barb (on mine, the coolant hoses are a larger diameter than the fresh water - don't know about the Twines?), then went to Supercheap and had a rifle through their heater hose section to find the hoses I wanted. For one of them I'm using a Camira hose, because it has a tight bend moulded into it right where I needed it - beats kinking a normal hose. I run heater hose for the fresh water as well as the coolant - I had the normal garden hose stuff that comes with the kit, but after a year's use it was all discoloured from the heat and half-melted. I'd strongly suggest using heater hose from the get-go.
Another thing I'd really suggest is to look at GG's setup here with the mixing valve incorporated:
http://www.myswag.org/index.php?topic=3268.msg382695#msg382695Mine:
http://www.pcoa.org.au/forum/viewtopic.php?f=19&t=4883And the original here:
http://www.expeditionportal.com/forum/threads/43197-On-Board-Hot-Water-Install-for-ShowerIt can be hard to get a hold of that particular valve in AU, but it's worth the effort. For mine, it removes the only downside to a heat-exchanger shower setup and makes it heaps safer for other people to use your shower without scalding themselves. Also, you save a whole heap of water.
The only other thing is that I spent a lot of time and effort trying to source quick-disconnects for the water in and out. You can use normal Nitto air fittings, but they rust out. You can get stainless versions, but they're terribly expensive. Either way, they reduce the flow rate because they're so tiny. There's some other types of couplings that are rust-proof but even dearer. In the end I went with normal hose fittings - a plastic one on the intake and a brass swivel one from Bunnings on the outlet. Both have been fantastic, they don't leak, they don't suck air like everyone says they will - they just work and are compatible with every other hose out there.
I also bought a whole heap of brass elbows, t-pieces and such for a king's ransom from Pirtek. I ended up only using two of them on the hot side of the shower - all the fittings on the cold water side as normal plastic sprinkler-system fittings from Bunnings. They're heaps lighter than the brass ones and so don't need to be secured. Just another case of me over-thinking a simple job when the simpler/cheaper option is actually much better.
Good luck!
Matto