It was only 10 minutes to complete the second half, so it's not that bad I guess. Still takes too long without automation though.
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EDIT: In terms of filesize, a stripped map with only the specific geometry and a light_environment to provide lighting information was 19.5 KB. A func-detailed version in brushwork was 20.9 KB. Assuming that the majority of that filesize is overhead for the basic map structure, it is interesting to note that the displacement version is cheaper. Both will have the same vis information, so why is the brush based version 1.4 KB more?
I'm guessing part of it is lighting information, seeing as displacements and brushes are lit differently. There's also the possibility of different bsp-structure (not vis structure!) for collisions etc, but I'm not sure. Anyone have ideas?
I figure it's 128 tris for the displacement version and 32 tris for the brushwork version, so in terms of basic geometry the brushwork should be cheaper. I'm going to try a fullbright version next.
EDIT 2: After compiling with no lighting I can confirm that the lighting is most of the discrepancy.
Fullbright Displacement: 18.0 KB
Fullbright Brushwork: 17.9 KB
EDIT 3: I compiled with no VIS because I was curious, and the filesize dropped again. Both versions were 16.9 KB. This seems a little silly since theoretically both versions would have been empty cubes (because neither displacements nor details cut vis) but clearly that was not the case.