Ya i did it in a 135 and will do it in my 450. I wouldn't do it in a small tank but most of the time 2 can get along. I've had a potters and a flame together and a flame and a coral beauty together with no issues whatsoever.
Known several who have done the coral beauty/flame combo without issues. Obviously all individual cases are different but saying stuff like they will hunt each other down to death no matter how big, etc. is just misinformation.