Thanks, that video helped enough. For the Constrictor, you need to build a small platform to have it rest on, I found 1 brick 2 plates construction high on the back of the bridge works. Note that for the Constrictor, the open ends should not point up, but 90 degrees to the side, otherwise the hinges of the upper panel are in the way. The main difficulty really is that you don't have space to see, there is too much detail of the superstructure in the way.
I am already looking forward to the other half
Other than that, fun build
Correct, the 1x6 plate under the 1x6 tile just popped out for me. It also looks good without it.