I have always found that Eheim Classics are hard to use with inline equipment due to the design of the outflow from the canister. If you put anything too close, the tubing always kinks.
I finally bought myself an inline heater which I have avoided because I just don't know where it will go. I also have a 9 watt UV sterilizer and an Atomic inline CO2 diffuser. Add the quick disconnects to that and I am quickly running out of room. To further complicate that, I am using lily pipes which I would like to keep on one side. They really need to be on the same side as my canister as well.
I can only use one side of my 20 long stand. It's about 26 inches of vertical space, 15 horizontal. I believe that the heater is the only thing that needs to be mounted vertically. One thing that is irratating is my UV has inlets on the sides, not flow through top to bottom.
Here is what I have now. You can see my space is pretty limited. Just looking for some ideas. If you have your own examples of how you did it, let me know. I am very much into keeping my plumbing as clean, short and simple as possible.