[Robotbeat]

This isn't true. If you want to keep making these claims, you're going to have to provide a source. For instance, there's plenty of space behind the pilot that is empty. There's plenty of interior space as the batteries are placed below.

Additionally, they are using bulletproof flight-certified batteries which are much lower than the typical good lithium ion batteries used in, say, a Tesla. They're just for the prototype. "“These are batteries that NASA is using, but they’re not batteries that we’d use if we were going to try and make it economical to fly today, because they’re very low in watt-hours per kilogram,” explained McDougall."

The electric motor (not an engine) is 560kW, almost twice the original 336kW radial motor, so it's not in the least underpowered (as you imply).