I didn't remove the scales, but I sanded them, mostly on the sides with 60 grit sandpaper. It roughed them up a little, but really didn't seem to help retention that much, so I took a file, made vertical "grooves" across the handle, and went back over it with 60 grit. Significant improvement in grip security...
Here's the handle on my Patrol Machete. The flash makes it look lighter than it really is, but it didn't show up well with it turned off. I've yet to take the scales off and do the top, but plan to shortly:
edit: I also plan to make the grooves a little wider, and maybe deeper. Have to look at them again when I take them off to see how deep I'm comfortable going, though. I like this even better than the cord wrap I had previously done on this knife.