If the Rocket is a 540 deg triple, I'm not sure that you will ever get the "loping" sound that you are seeking. I don't care what other people think but I like the "sound" of a Harley. Nothing sounds better than a well tuned HD. I don't expect or want, however, to have my Rocket sound like that.
I would like for a Rocket exhaust system to achieve a deeper, more throaty sound. I have the Staintune 3-1-3 system and it's deeper than stock but not quite where I would want it to be.
Good luck with trying to find a solution. I'm sure there are others that will be watching.