So that's what you needed the 4x bricks for.
Looks amazing btw.
Actually I didn't use them. Had I used them where I needed them it would have broken up the texture pattern. Any way I tried it didn't work. You can see a 4x hole in the light rim on the wall in the second last image in OP. I had to remove the textures from the rim to make it work as you can see from the latest images.
GSF was right, the textures are based on an 8x8 scale and anything smaller than that will break up the pattern. They're useful for smaller details though.
I'm using 4x print cubes at the moment.