I think you may have a hard time finding something 'between' a Paradigm Domination and a Tropical Heat Pearl.  They are both the same cover (Reactor Pearl) but with a huge difference in cores.  All of Storm's R2S balls will be different enough not to really get you something in the middle.  I would suggest instead of trying to find something between you should probably look for a medium RG solid to give you a different look at the pocket. Something like a Manic, 2Furious, or even a RotoGrip Shooting Star will give you an earlier roll with a smoother backend reaction.