So maybe this is just a rough and tumble species. I still am holding out hope for mine despite their close proximity in size. About two years ago I obtained two large chrysopterus from a local wholesaler in hopes that there was a slim chance that they might pair. I placed them both into a 20 gallon tank for quarantine. I assume thew were both females because without even getting themselves acclimated, the two fish were biting each other's fins and removing scales. I subsequently seperated them with a see through divider and tried several times to reintroduce them with the same results.
With my current tricinctus it is a very different story, the smaller one of the two seems to be going through all the signs of submission shaking, biting at the substrate, etc..
This seems to over just fine in the small tank, it's just in the luxury suite that the larger of two finds this behavior unacceptable. I have never had clowns behave this way. Then again, I have never kept this species before either so no matter what happens I'm chalking it up to a learning experience.