My modular Sewer Tunnel is now available in Gumroad for Unreal Engine. The tunnel pieces snap seamlessly grid with tiling textures. It was quite fun to test this in the engine with automatic collision.
Lightmap UVs are set for each modular pieces, so there should be no shading issues even with lower values in Lightmap resolution settings. So many asset makers ignore this step resulting in poor lightmap UVs and unoptimized result. Lightmap UVs should be as continuous as possible and non-overlapping which may not be not what one wants to do with texture UVs.
I am thinking to expand this by making X section as well.