I've also tried down to 178 but had the best luck with the 212 ELDX. My barrel is 1/8 so I can imagine your 1/9 might have better luck with the lighter bullets.
I had to back down on the load for the 178 ELDX as I was getting pressure signs running 3215 ft/s. I tried the 212 ELDX with Retumbo and they are shooting really good. I have not ran it through the chronograph yet.