It's certainly not going to happen, but I tell you anyway: stick to one razor, until you can get consistently the same shave over and over again. The EJ89 is a great razor and you should be able to get consistently great shaves with it - of course you have to ditch your Feather blades first - they only work in the Feather AS-D2 unless you are Obi Wan, Yoda or Darth Vader
I know, you want to try your new razor, so you won't follow my advice, so here is the next best thing: just use one base plate (probably No 4) of your new razor and stick with it, until you get consistently the same good shave out of it
Again I fear, you won't listen to me, you will try at least 3 if not 4 plates of the Rockwell, so here is the last piece of advice (for tonight at least): the right angle will be different for every razor you try - and this includes every different base plate of the Rockwell - yes that is correct: the right angle for Plate 1 is WAY different than the right angle for Plate 6
So how do I know you won't listen to most of this? I've been there myself