Generally Argentina get nasty as they grow.You could try it and see how things work out but I would not advise it.
Beautiful hets by the way.
I think you stand more chance with the micropthalmus.
Hmm...in that case I was misled by the store that sold me the Argenta. He showed me his group of 3x 9-10" that live together in a 120g and said they are mellow. Only paid $7 for it, so I could easily sell it. Any ideas on a single large-ish, fairly mellow CA I could replace it with?