So after gridding out Kryptos K4, an idea occurred to me.
Perhaps my additive was right but wrong. If it fits as a grid then maybe lining up SOTPYRK would be similar to the CT on the left and decryption thingy on the right found in the copperplate proper. It’s a stretch but humor me for the next couple weeks. If you’re not interested, check back in 3 months =)