A good point in the comments that you would most likely not have unrestricted access to the back of the tag for the shim as it SHOULD be pulled tight but it still does not appear as secure as one would hope.
Is this a "works as designed" system? Meaning: designed to get exploited...
FTA: "Bernhard, however, said that although voting machines may be locked when they are stored in the county clerk's building, they are left unattended for days at polling places—high school gyms, churches, and community centers—prior to elections. "
