Here's a pic of my bong cooled system from March '04.
Notice the silicone tubing going the last 5" from tubing to blocks...that's about absolutely necessary to let the blocks align properly without any lateral stress. If you're not good to the millimeter in your tubing skills, you'd best look to do the same. One imperfection and you'll get high temps or even burned chips due to a bad thermal interface from block to chip.
For info's sake, that's 1/2" bendable refrigeration tubing with 3/8" copper pipe fittings--a perfect match.
Notice on the tubes out the back you'll see that I used brass compression rings to make the tubing into hose barbs for the silicone interface. It's the same on the tubes inside, only with one ring per junction.
The brass rings are also called ferrules, and they are available in a 10 pack at Lowe's/Depot for many different sizes. That's the same way I make barbs for my home-built or re-engineered blocks.
As a bong cooled system, it was running at about 2C above room temp for the cpu, so don't all of you go off about the elbows and T's.
And the 1/4" x 1/8" passages of the NB block made sure that the processor got the flow it needed..
*Almost forgot..I use copper tubing in my current rig, routed behind the motherboard in my custom case.
Just search for "Further" with my username to find my thread and pics.