Is there a company making high-quality lever perches (the type with a mirror mounting hole) that don't eventually fracture? I think I've had about four fractures of Emgo perches. Yes, I understand the economics of production for a limited market, and the Emgo product fills a need.
I don't believe I've overtightened the clamps because I line the loose "U" with a bit of innertube so less screw torque is required to grip the bars.
Richard L.