There is currently significant interest in the design of small electric vertical take-off and landing aircraft to alleviate ground traffic and congestion in major urban areas. To support progress in this area, conceptual design methods for electric single-main-rotor and liftaugmented compound helicopters previously developed by the authors have been modified to include improved battery and propulsion system models. The updated methods were used to reinvestigate the feasible design space based on varying mission profiles and technology assumptions. The results show that the energy capacity of the battery drives the battery sizing, rather than the power requirements. Improving the propulsion system models also increased the bounds of the projected feasible design space and enabled an additional study into the potential benefits of decoupling the main rotor from the tail rotor. This study showed that decoupling the main rotor and tail rotor has the potential to reduce the total mission energy required by between 3% and 35% depending on the mission distance modeled at the conservative future technology level. A comparison of the single-main-rotor and liftaugmented compound helicopter configurations was re-examined, and it was found that there is an increase in the region in the design space where the lift-augmented compound helicopter is the more energy efficient helicopter configuration.