Ah, so they are inside, the set of 4 and it's just the rears that are on the outside. OK, the photos help immensely. So it's really the heat sinks themselves then that were are removing, I'm assuming in order to get to the pesky screws I can see that secure the faceplate to the front. When I read in the instructions about removing channels I figured it was referring to some other component actually inside. It never occurred to me this was a reference to the heat sinks. I see the faceplate attaching screws are very close to the 1st heat sink fin, with no room to access them via a screw driver etc. thus why the heat sink needs to be removed.
Thanks for the warning about how to pull the heat sinks out.