Avoiding too much preload on the bearings if why Shimano's TL-FC16 is plastic and small in diameter. Unless you use pliers on the outside edge, you really can't badly overtighten it. I always make sure the driveside is seated fully against it's bearing by smacking it with the palm of my hand or rapping it lightly with a rubber mallet. Then install the nds arm (and the spacer for a triple), thread in the compression plug and tighten it just snug using TL-FC16 and not really cranking down on it. Torque the clamp bolts evenly in stages to spec.

Done that way I have many thousands of miles on BB6700 bearings with no failures.