Well, I got to the bottom of the thread and to my suprise, no one has mentioned the kole tang. They stay smaller, and don't crave the open space as much as say, a yellow. A kole should do fine in a 55 (though I can't say that from experiece), but it should have plenty of LR to graze on and hide in.
Also, I'm in total agreement about the last few posts about the clown trigger.