Construction of roadbed

For the big loop of my mainline, I need to run a double mainline around a room where there are no walls to fasten any benchwork to. In addition, the track has to maintain a constant gradient of 1.6% along the length of the loop.

I wanted to minimize the 'bumps' that can appear when track transitions from one support to another so I have decided to use 3/4" plywood that is firmly screwed onto vertical 2x4 pieces of lumber. I am hoping that the strength of the 2x4 lumber will prevent any sagging and warping over time. Here is an example showing how the tracks will sit on a wide roadbed.

In order to adjust the gradient of the roadbed, I support the 2x4 with some threaded rods. These allow fine adjustment of the height of the track.

I have constructed support for about half the loop so far....