Hiscaro,
I played around with your files a bit, and I found that the isosurfaces at 0.01/-0.01 look pretty similar to what's in the orca documentation. The orca page doesn't mention what they set the contour value to, so I'm not sure if this is exactly the same. I also recalculated the cube files with orca_plot using a 100x100x100 grid, as the default 40x40x40 was coarse enough that I had trouble seeing the smaller lobes.
Here's the command I used to set the isosurfaces and colors:
volume #5 level -0.01 level 0.01 color #0000ff5c color #ff00005c
(the result of the volume subtract command was in model #5)
I've attached images showing the fukui functions with these settings. If you have any other questions, let me know.
Best,
Tony