Thanks all. I have to agree on the plastic track being a great find. In fact, I like it so much, I have decided to use it in more places than I originally planned and will likely need to go back and get a few more.
I made some progress on figuring out the basic core design for my hallway/platforms.
First I cut a bunch of strips of foam core to use as stock when I am making my platforms. I made a bunch of strips as tall as my wooden frames, and then some 2 inches wide, 4 inches wide, and 5 inches wide to match my three platform widths.
My foam core is only 20" x 30", but my walkways are 48" long. So to make my long walkways I need to tape two pieces of foam core together. I trim both pieces 24" long so that the seam is in the center of the board. I use wide clear packing tape to hold them together, but only on the underside. Paint likely won't stick to the tape, and I will be adding other elements to stiffen the walkways so I don't have to worry about taping them only on one side allowing the joints to flex.
I then cut a length of my plastic track and hot glued it a half inch in from one side of my walkway, making sure to center the pattern at my joint, and being sure to leave a space at each end where the walkways will be on top of my frames.
A quick test fit showed this worked well. It gives a nice look when viewed at a slight angle, and it already stiffens the walkway quite a bit.
I have ordered some battery-powered LED "holiday" lights that I will glue to the underside of these walkways. They won't give out a lot of light, but hopefully these tile strips will give the light a nice pattern.
I want to completely assemble all the walkways and lock them together into a single unit before attaching anything to the base frames. This will let me do some pre-painting of hard to reach areas, and it will let me rig the lighting before everything is glued down.
As is, the walkways are still really flexible and slide around a lot. To help hold the walkways in place while I work on fitting everything together, I glued on a few pieces of my foam core stock that were pre-cut to the same height as the sides of my frames.
I then used one of my spare Battletech bases as a guide to cut out some angled foam core to form some support pillars for the middle of the walkways.
I like the results. The walkway looks good, and it is nice and solid. It won't take any gamers leaning on it, but it will hold up to any normal play.
I then made another walkway just like this one for the other side of the map.
For the center walkway, I used thinner 4 inch wide foam core. This let me have two outer 5-inch wide walkways, with two 5-inch wide "engineering" gaps, and a 4-inch central walkway (for 24 inches total).
The middle of the central walkway will hide the battery packs and controls for the lights, so I made a solid wall area in the middle of the central walkway. (Later, before gluing everything in place, I will cut an access hole in the bottom of the wooden base so I can reach the switches and change out the batteries.
With all three main walkways resting in place, I can get an idea of how this will look. There will still be some 2-inch wide walkways along the short sides, but this is the main look. I think it will work well.
I was eager to get an idea of how this might look when lighted, so I put a flashlight under one end of one of the 5-inch walkways and turned out the lights. This is much brighter and more localized than the final holiday lights will be, but I just wanted to see.
I'm glad I tested, because this foam core let far more light through than I expected. It will get painted in the end, but to ensure that light does not penetrate where I don't want it to, I will likely line the undersides of the walkways with foil before installing the lights.
To see what that might look like, I plopped a spare piece of wood down on top of the walkway and turned the lights back off.
There will be more shapes to get shadows off of, and colors to pick up on (possibly including colored plastic over some of the bulbs), but I think this will work well.
By making my three main walkways into "light boxes", I will be able to cut into the walkways anytime I need a light source for a piece of 3-D embellishment glued on later.
With my basic layout nearly done, I will finish the 2-inch walkways here, and then repeat the process on the other hallway map and on the half-hallway portion of the bridge map.
Back to work.