Our Conventional Standard Bisley has an extra 16th of an inch of material around the outer perimeter of the frame. This is the one that really started it for me. It also has another 1/8 of an inch along the inside Perimeter or what we call the inner cut, so that you can thin it down forward as well, without loosing the platen face that is necessary for the grip panel to rest on!
For images of Grip Panel Materials available click this link - Grip Panel Materials