I have a 12" Lynx and MTC. I use knife point cutting in the KNK plug-in as Elizabeth suggested and it has solved all of my positioning questions/problems.
In MTC, I created a custom mat, named it Lynx and gave it the dimensions of 16" x 12" (my mat is an orange cougar mat). When cutting designs, I place my paper anywhere on the mat and put my knife point in the upper right hand corner of my paper and hit the origin button. That is now the upper right hand corner of the design box that surrounds your image on the MTC screen.
KP.jpg
If you want a true 12" cut in both directions, are you using paper that is larger than 12 x 12? If so, try it with pen in your blade holder first and set your mat size as 13" x 16". This will give you a half inch of clearance on either side before you hit the margins.
Make sense? I hope I haven't made it more confusing.
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