So it turns out that if you take Kryptos K4 and reverse it and then attempt to remove an additive of the letters KRYPTOS, it is exactly what you’ve done before.

Take the end of K4:

AUEKCAR, I’ve already done the math on trying to remove the additive SOTPYRK

Now take the same and reverse it as I just did trying to figure out how to manipulate K4:

RACKEUA, and the letters I was going to remove were KRYPTOS

Took me a couple minutes to realize those were the exact same operations.  I’m going to go ahead and skip the math on this one since it’s already been done.

I find myself temporarily out of ideas…

Maybe I should try transposing K3+K4 after all…