i will have to disagree with your disagreement as i have kept red heads quite happily with more aggresive cichlids for example a JD, a PAIR of convicts and there was no problem size wise they was all similar maybe give or take an inch.
most people disagree with putting the more aggressive cichlids with fairly peacful ones but each cichlid has its own personality so its hit and miss tbh.
Agreed all cichlids have personalities and if its worked for you great but you have to agree there are better suited cichlids to this tank and better suited Geos than the redheads. I can see how it would work with a JD and cons maybe but its the texas and the sal that I would worry about most with them.