So I have two EOS 3 bodies and one of the reasons I got it was because of it's ability to track my eye movement and predict my desired focus point. In practice, however, since I wear glasses it's been more of a frustration than anything else. I know others have had success with the system, however. My understanding is that I can insert an eye piece into the camera so that I can take off my glasses when focusing. Is this true and how (precisely) does one go about this?