I think adding the extra hole in the back side improves the trick immensely, because then it's "obvious" how the die got through the back ("it went through the hole, dummy") and leaves people focused on how it got through the mirror, which is exactly what you want them focused on.
Great show Don. Thank you for showing this miracle. I will build one but not with a dice. I will use a small bone. Nice stuff for halloween. The magic bone of a witch or something like that. Sort of a witch test. A normal bone will not pass, but the bone of the witch will pass. So we can prove, that it is a bone of witch we got from a grave :-)
Just finishing building my new workshop - retirement is on the horizon. I will be indulging myself by having fun making your wonderful illusions. Thanks, Don.