altitude = ((fractalfunction + prescaleoffset) * worldscale * roughness) + offset

FT is limited by having a whole-world editing grid that is necessarily limited in resolution due to other implementation details. This editing grid is used in conjunction with the specified fractal function to generate the final result whenever the map zoom or pan is changed. Wilbur has a fixed-size editing grid that is never regenerated; what you have is all you'll get (it just gets blurrier as you zoom in).

FT's documentation could indeed use some help.

MDR input was broken in some versions of FT. I can't recall which ones, though.