By GT do you mean Green Texas or Green Terror? If its a Texas and its a male then yes you will get fry because your flowerhorn looks female. Flowerhorn are CA hybrids and all CA cichlids can interbreed. If its a Green Terror then don't hold your breath because they cannot interbreed because its a SA cichlid. The only SA that has ever been proven to hybridize is the Festae.
Good call Chris! I have been so focuses on my green terrors recently I forgot that GT is also used for green texas, thanks for bringing it back into my head again.