Bob W, the answer to your question is that the rear of the anchor plate should actually settle into the palm of your hand with the string butted up against the front of the plate, thus insuring consistency of grip (assuming you're using a deep hook.) Most people when they switch to a competition tab like the Cavalier wrongly assume that the tab should completely cover their finger tips. However, after you've shot a new tab for a couple hundred shots you'll begin to see precisely where the string comes off the tab. I then trim my tabs to about 1/8" just before that spot, which leaves my fingertips exposed; but they never touch the string as they are flicked out of the way during release when you relax the hand.
Drewsbow, the metal piece you removed was not a thumb rest, but rather a chin ledge used for an under the chin anchor.