Ewww...that's a tough one! That Achilles is going to be MEAN!
I had a Powder Blue, Tomini and an Atlantic Blue together, in my 200 at one time. They actually all got along fine, even though they were all added at different times. The Powder Blue regularly got into it with our One Spot Foxface though. Later, the Tomini started picking on the same Foxface. Every few months, the Foxface would get have a nice, deep slash across it but would always heal up.
If you're sure about the two additional tangs, you're definitely making the right choice by adding them at the same time.