I turned the angle bar around 180 degrees quite a while back so that the angle adjust ment is continuous rather than stepped. The locking screws contact the flat... undrilled, surface of the bar. I also flattened the tips of the locking screws, but I don't think you need to do that. I admint, I use a set of pliers to add a bit of torque when I tighten the locking screws. They don't slip
This all is pretty neccessary when one uses an assortment of stones with varying thicknesses...and wants that 0.1 degree repeatability (on the angle cube readout anyway).

Phil