Just a note: There is no 1 correct way to do a veggie system. If you decide to make a system different than mine, that doesn't mean that it's not the right way to do it.
Here is what i use in my bus instead of "tricore" fuel line from greasel.com
I swap coolant/fuel lines in my setup.....In the photo the coolant flows through the small inner pipe, and veggie in the outter larger pipe. I didn't like the restriction this put on my coolant system, so I run the coolant through the larger outer pipe (it enters through the 90* elbow)
this idea is not mine, but i forgot where i originally saw this heat exchanger. I would guess that it transfers at least 100 times more heat than the rubber/plastic tricore from greasel. Copper is an excellent conductor of heat. The disadvantage of this particular setup is that it is not flexible.