I've heard a number of different things regarding the Unsharpen mask option scanning in Flexcolor.
As far as I know, there is no way to turn USM off in Flexcolor (still). The only way to defeat the built in sharpening is to set it to a -120. That setting effectively turns it off.
Then you can do capture sharpening in your other application of choice (I tend to use PKS2 but hey, that's meľand ye I am involved in PixelGenius :~)