Here's a tip, lads.

If you want to use only an upper part of a midtexture and recede it into the floor, then the lower part will render through the floor in software renderers. EXCEPT, if the surface it's trying to render through is a different brightness, in which case it'll be properly hidden underneath, thus if you make a tiny sector along it which is only 1 unit of light different, you'll get the seamless visual.
>general sector is 176 units of light
>one side of the fencing here is 175 units
>the other is 174
1 or 2 units of light is so subtle that it's imperceptible, so it looks perfect. This should also work for the lower parts of textures up into the ceiling.

Remember to mark the linedefs to not show on the automap for maximum cleanliness.