Slab. Not a good idea. I agree that it is ugly and not really necessary, but if, God forbid, an AD should occur, and that safety was missing, you know whose butt would be in that proverbial sling.
I have one on my Mod. 94 in .45 Colt. I ignore it until I want to remove the ammo from the gun. Then I put it on to run the rounds out of the gun. If the hammer should slip, IE, I screw up and hit the trigger, that safety will prevent an AD. Just my .02.
Paul B.