CRutkowski,
Since surface is a much more responsible for ball reaction than RG Differential, I believe you are focusing on the wrong piece of the ball's specifications. Most balls (not all) with a diff of .030, will probably be as strong or stronger than your Blade Pearl.
Try looking at the Roto-Grip Sonic-X (solid or pearl) or the Dyno-Thane Barrage.
Other possibilities are the Columbia Wild or Scout/R, Brunswick Power Groove, Ebonite Tornado, AMF Courage and Xtreme Courage and Storm Big Hit.
The Ebonite V2 Dry has almost no differential and it can posisbly fit here also; but it is more expensive than most of these others.
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