Baby steps. However, the sums don’t look as bad when you take into account:
It was replacing a Wasp Junior, which weighed 300kg and probably turned fuel into useful work somewhere in the 10-20% efficiency range (and less out of optimum power band) to make 450hp, with a 750hp electric unit weighing ~130kg at >90% efficiency. All the pipes, valves, generator, induction/exhaust, filters, controls, etc. can be removed which I’d guess is at least 50kg; you do need a power controller and wiring but because it’s fairly high voltage it’s not like huge bus-bars. That leaves space for ~200kg of battery before you get it to the dry weight it was before conversion.
For short hops there's no need to waste fuel to warm up the engine, there’s instant power available and maintenance should be less of a problem as the electric motor doesn’t care how many times it’s been started and stopped. Doesn’t need plugs and oil, either.
It’s obvious we won’t be getting transatlantic electric passenger aircraft for a while but this would seem an ideal place to start and see where the tech takes us. There are plenty of places where a quiet transport doing 10-20min legs would make a lot of sense...