what exercises should i add to get more size on these bitches?
Eh, triceps kickbacks, with a 3 second squeeze at the top obviously?!

Heavy weighted dips and underhand chins give the arms a thick look. Plus, they'll be as strong as hell doing these. I always felt that certain elbow extension movements helped to back on meat around the triceps right above the elbow joint but I'm not sure if this was actually the case or if it was just me being delusional... Try the JM press as an example.
In all truth though, I would say just consistently continue what you're doing, its obviously working and they are growing so if it ain't broke and all that...