Continued working on the guts of the project. Glued the tunnel liner to the side rails, which took a bit of time, mostly because I only have a pair of large spring-clamps (got a ton of the small ones, but they are too small). The thing is quite strong now.
Then I added a pair of supports for the "plateau". I cut them using the template I made for the portals. I was going to trim them so they fit down tight over the tunnel, but decided I needed/wanted more height. By lengthening the tunnel from the original, I realized I was effectively flattening out the hill. I want this thing to have more of a pyramidal scale/appearance, so to do that I jacked it up a couple inches and slightly expanded the footprint of the "plateau" (which has been cut and is ready to go). Other things may require a bit of scaling upwards as well.
The supports are attached using a healthy dollop of Titebond and four 2-1/2" exterior screws.

I think the next few steps will be to (1) sand the face of the portals to remove any liner that's sticking out because I didn't trim it close enough, (2) paint the interior of the tunnel black, and (3) cut and attach the thin plywood or masonite base(s) on either side of the tunnel. After that, I think it will be safe to attach the "plateau". The trick will be getting the tunnel base(s) plumb to a flat surface and keeping them that way when the "plateau" is attached.





