I've had a 24" Woodmaster drum sander for around 5 years in my home shop. I
have never had a problem with it rounding over edges or leaving knots proud
of the surface. The hook and loop backing on the paper and drum isn't that
thick. The loops on the back of the paper especially are more like "fuzz".
When rolling new paper onto the drum ther is basicly no give if you are
carefull to get the paper tight when installing (turn the drum with one
hand, pull the paper tight with the other). Of course, I mostly use it for
finish sanding and make light passes.