Randy,
It really depends on how the tunnel is constructed inside. If you have a tunnel lining, then things become overly complicated.
I plan to illustrate my tunnel treatment soon. Rather than full cat wire assemblies, only the 2 messenger wires over each track will continue into the tunnel. Attachment to the layout will simply be vertical TIG rod hangers inserted into portal ceilings and wooden frames spanning the internal tracks. The tight fit tolerances I get by inserting the rod into a predrilled hole of correct size, assists in holding in place the initial alignments and levellings. To permanently attach, mark posititions and remove the hangers and messenger wire, epoxy the hanger holes and reassemble. Solder the messenger to the hangers and enjoy.
Transitions in heights of the messenger wire are as necessary in our compressed little worlds as with 1:1. Fortunately, most of the pantographs on our models operate under spring loading, so they follow a dipping wire until almost fully collapsed. Pennsy through the Hudson River tube barely had room for the pans of a GG1, even after the tunnel was modified to fit their modern electric fleet. So goes it with other obstructions to catenary like overpasses, bridges and even signals. While the majority of the line will have messenger wire just low enough to place pressure against the pans, transition sections in advance of obstructions will smoothly collapse pans to lower than normal....and again raise them to normal upon exiting.
Pantographs on real Pennsy equipment could deploy much higher than normally replicated in scale by our models. I have a pair of old 2 rail BB1's that can extend that tall...I've found they are an exception.
Hope that helps somewhat until I get back to posting.
Bruce
