Obsession pretty much nailed it. As long as you stick to the Lugubris pikes you should be fine. Really, some of the Saxatilis pikes would work well as well, but you are probably going to have better results with the Lugubris pikes.
What is the availability there in Aussieland? I know of a few people that keep Crenicichla johanna there, but haven't seen much aside from that.
Hate to bring a month old thread back to life but I keep a 14" Lenticulata with my wild caught Mono, Orinos, and Kelberi and he holds his own VERY well. In fact I would say he may be the alpha in that tank, and thats saying alot being in with two 12" Orinos.
Some of it will be based on the temperment of the individual. I have two 12"+ Lents
that are getting bullied quite a bit by a 10" Male Zonatus. Had to put a divider up as he (Zonatus)
was becoming hyper dominant.