Thanks to both of you. I've always looked at the Shroud and the Sudarium Christi as mystical gifts left to us by our Lord, they humble me and fill me with awe (and shame and sadden me when I see His wounds), but neither are necessary for my belief in Him. I, selfishly, never looked at the Shroud or the Sudarium Christi as you both do - and you are right, they do have the ability to convert non-believers, as evidenced by your posts.
Thank you again.