It's aparently tricky to do. I have the same set up, only my EBJD was added a few weeks before and was larger than the JD I added (by like .5" or less). The way I see it, the EBJD is supposed to be less mean (mine is not) so for best results you need to add him first. Do you have a second tank or quarantine tank? If so I'd try moving the JD there for a few weeks and re-doing the 55. This will hopefully make the EBJD feel more in control when you re add the JD in a few weeks. Again, lots of hiding spaces, you can't have too many.