Hi Tyler, before you trim it make sure the the kidney is the right side up. The MTK armor, I am not to familiar with, but if its like ATA , the bottom edge of the kidney piece is a little longer than the top edge. The butt piece edge might be alittle shorter than the bottom of the kidney piece. When you hold the kidney piece against your back, the the edge that connects to the ab should be straight up and down like the ab piece edge. I noticed in your photo the top edge of the kidney is leaning forward. This could be the way you are holding it, just wanted to make sure.