It is not the contact area on the U that matters but the flat part against the metal doughnuts that grip it that provide the majority of the contact area.
A bigger issue is making sure your spade is soft. Hard spades or rhodium coated spades are too hard to grip when tightened and can easily come loose. Some of the best IMHO are the spring-loaded WBT types.
A bigger issue is making sure your spade is soft. Hard spades or rhodium coated spades are too hard to grip when tightened and can easily come loose. Some of the best IMHO are the spring-loaded WBT types.