Most companies lines maintain dynamic "integrity" down to 12 pounds. You will see higher RG's than the heavier balls for certain, but that is usually compensated for with higher RGDiffs.
The best cores in 12 or 13 #ers, imho, in current offerings...
ebonites "time" & vortex lines, brunswicks monsters & bvp's, & in Morich's TA & Ravage (if you want to go "upscale").
Another very good design still "out there" are some of the re-run Quantums that frequent ebay...
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