I had problems to get my Block soldered together as i told
here (I fixed it with using Epoxy now). The Block is based on the basic idea of BB2K and Cathars suggestions in that thread.
Because of the Problems I wanted to use that one for testing and build another one once again. The block I thought about is exactly what Cathar postet here. Honeycombed and with pipes as jets not just wholes in the middleplate.
This shouldn't be a big Problem. Use a Copper middleplate and drill holes in it. In these holes we can easily attach small copper pipes. A little Hammer is all we need