Biocatalyzed electrodes offer fast and robust conversion of a wide range of fuels to electricity. Significant conversion rates require high catalytic loading, which often leads to transport limitations in biocatalytic electrodes. We have previously reported direct growth of carbon nanotubes onto carbon fiber for glucose-oxidizing bioanodes leading to increased catalytic activity by factors of four over bare carbon paper. In this paper we discuss the tradeoffs between carbon surface area, porosity, and electrode thickness, and discuss contributions of these parameters to optimal catalyst utilization and electrode performance. Simulation results will be reported and compared with experiment.