Radiused sanding blocks are fine for sanding wood in order to get the radius on the fingerboard, but I don't see that they'd be precise enough for fret leveling. What I mean is I'd be concerned about twisting the tool as it's being coaxed back and forth, which would change (tighten) the radius and not hit everywhere. Then you're dragging it around a lot more than you need to and taking too much metal off of the outer edges of the frets. And for the record I have no problem with snakes in my shop. Probably a professional courtesy (lawyer by day).