Not really signal integrity is paramount with these sort of signals, just stick to the proper cables and connectors. I don't understand why you want the signal to go through the copper rods, even for artistic reasons, its going to mess up the signals, so forget the idea. I would look at a far simpler signal, say basic audio for going through some copper rods as you describe. The main problem is the signals are LVDS (low voltage differential signals) that need to be transmitted over twisted pair cables.
Have a look at return currents or even better a basic search for signal integrity (or differential signals over twisted pair cable) will provide some information on what is happening, though the concepts are a bit above basic understanding of signal propagation.