The 'crater' works good for me. I make a short, shallow flat spot, then bore in a dimple with the tip of a dremel grinding stone. (I just grab a dremmel and a motor and go at it. yes grind at right angle so the shaft doesnt spin.)

I then blow off any metal dust that may have stuck. (I'll do a plastic bag next time :) )

I do not like long flat spots, they unbalance one end and make the shaft wobble. Also, I use the motor fror braking and a flat spot always seems to leave a little 'play' and this ALWAYS loosens the set screw for me.

This with plenty of LocTite is the ONLY thing that works for me so far.