How about a mid-size pike cichlid? I have one with my GT and oscar and they all get along fine - see http://www.cichlid-forum.com/articles/intro_pike_cichlids.php
I'm not saying it won't work, I'm saying its not what I plan, would do, will do or recommend.I'll just share what mixes I'm thinking about.
I already have the Oscar and Pleco, so their automatic for me but you can substitute just about any sm-med cichlid not too aggressive for the Plec.
I wouldn't mix the RT or JD with the O, but the GT, Sev, FM and alot of other smaller cichlids are OK