Processes are provided which include copolymerization using two different metallocene catalysts, one capable of producing high Mooney-viscosity polymers and one suitable for producing lower Mooney-viscosity polymers having at least a portion of vinyl terminations. The two catalysts may be used together in polymerization to produce copolymer compositions of particularly well-tuned properties. For instance, polymerizations are contemplated to produce high-Mooney metallocene polymers that exhibit excellent processability and elasticity, notwithstanding their high Mooney viscosity. Other polymerizations are also contemplated in which lower-Mooney metallocene polymers are produced, which also exhibit excellent processability and elasticity, while furthermore having excellent cure properties suitable in curable elastomer compound applications. Many of the contemplated polymerizations include controlling the ratio of the two metallocene catalysts used in the polymerization so as to obtain the desired Mooney viscosity and desired rheology (indicated by Mooney Relaxation Area) of the copolymer compositions.