You won't damage the bearings or race by pressing on the bearings to install the cups. The King adapters simply provide a better fit for the various available presses. You can accomplish the same thing by modifying some washers or wood blocks if it's even necessary. Ideally, you'll get a tight fit between your adapters, your forcing screws, and the headset so that there is no chance of the cups getting cokced sideways a bit.