Cal 21 keel question

I've been looking at small trailerable boats and of course the Cal 21 deserves a serious look. I'm a little confused as to how the keel is designed to be sailed. Am I corrected that boat is designed to be sailed with the keel full down and locked? Can you sail it with the keel half down? I assume the disadvantage here is drag from the cable and in the event of a capsize possible damage to the boat from the keel impacting the hull. Lastly, how about the keel plug? I'm guessing after the keel is down and locked you have to get wet to remove the cable and install the keel plug. Am I correct? Woody